diff --git a/tests/css-parsing-tests b/tests/css-parsing-tests
index 530ab15..88fc3fc 160000
--- a/tests/css-parsing-tests
+++ b/tests/css-parsing-tests
@@ -1 +1 @@
-Subproject commit 530ab150796b959240fb09eae3b764d8bae6d182
+Subproject commit 88fc3fc33986f835b6658b1b824b50c9550723f8
diff --git a/tests/test_tinycss2.py b/tests/test_tinycss2.py
index 0df3582..4580062 100644
--- a/tests/test_tinycss2.py
+++ b/tests/test_tinycss2.py
@@ -20,6 +20,7 @@
 from tinycss2.color3 import parse_color as parse_color3  # isort:skip
 from tinycss2.color4 import Color  # isort:skip
 from tinycss2.color4 import parse_color as parse_color4  # isort:skip
+from tinycss2.color5 import parse_color as parse_color5  # isort:skip
 from tinycss2.nth import parse_nth  # isort:skip
 
 
@@ -159,6 +160,19 @@ def _number(value):
     return str(int(value) if value.is_integer() else value)
 
 
+def _build_color(color):
+    if color is None:
+        return
+    (*coordinates, alpha) = color
+    result = f'color({color.space}'
+    for coordinate in coordinates:
+        result += f' {_number(coordinate)}'
+    if alpha != 1:
+        result += f' / {_number(alpha)}'
+    result += ')'
+    return result
+
+
 def test_color_currentcolor_3():
     for value in ('currentcolor', 'currentColor', 'CURRENTCOLOR'):
         assert parse_color3(value) == 'currentColor'
@@ -169,23 +183,48 @@ def test_color_currentcolor_4():
         assert parse_color4(value) == 'currentcolor'
 
 
+def test_color_currentcolor_5():
+    for value in ('currentcolor', 'currentColor', 'CURRENTCOLOR'):
+        assert parse_color5(value) == 'currentcolor'
+
+
 @json_test()
 def test_color_function_4(input):
-    if not (color := parse_color4(input)):
+    return _build_color(parse_color4(input))
+
+
+@json_test(filename='color_function_4.json')
+def test_color_function_4_with_5(input):
+    return _build_color(parse_color5(input))
+
+
+@json_test()
+def test_color_functions_5(input):
+    if input.startswith('light-dark'):
+        result = []
+        result.append(_build_color(parse_color5(input, ('light',))))
+        result.append(_build_color(parse_color5(input, ('dark',))))
+    else:
+        result = _build_color(parse_color5(input))
+    return result
+
+
+@json_test()
+def test_color_hexadecimal_3(input):
+    if not (color := parse_color3(input)):
         return None
     (*coordinates, alpha) = color
-    result = f'color({color.space}'
-    for coordinate in coordinates:
-        result += f' {_number(coordinate)}'
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
     if alpha != 1:
-        result += f' / {_number(alpha)}'
+        result += f', {_number(alpha)}'
     result += ')'
     return result
 
 
-@json_test()
-def test_color_hexadecimal_3(input):
-    if not (color := parse_color3(input)):
+@json_test(filename='color_hexadecimal_3.json')
+def test_color_hexadecimal_3_with_4(input):
+    if not (color := parse_color4(input)):
         return None
     (*coordinates, alpha) = color
     result = f'rgb{"a" if alpha != 1 else ""}('
@@ -210,9 +249,23 @@ def test_color_hexadecimal_4(input):
     return result
 
 
+@json_test(filename='color_hexadecimal_4.json')
+def test_color_hexadecimal_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    assert color.space == 'srgb'
+    (*coordinates, alpha) = color
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f', {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test(filename='color_hexadecimal_3.json')
-def test_color_hexadecimal_3_with_4(input):
-    if not (color := parse_color4(input)):
+def test_color_hexadecimal_3_with_5(input):
+    if not (color := parse_color5(input)):
         return None
     assert color.space == 'srgb'
     (*coordinates, alpha) = color
@@ -251,6 +304,20 @@ def test_color_hsl_3_with_4(input):
     return result
 
 
+@json_test(filename='color_hsl_3.json')
+def test_color_hsl_3_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    assert color.space == 'hsl'
+    (*coordinates, alpha) = color.to('srgb')
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f', {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_hsl_4(input):
     if not (color := parse_color4(input)):
@@ -265,6 +332,20 @@ def test_color_hsl_4(input):
     return result
 
 
+@json_test(filename='color_hsl_4.json')
+def test_color_hsl_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    assert color.space == 'hsl'
+    (*coordinates, alpha) = color.to('srgb')
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f', {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_hwb_4(input):
     if not (color := parse_color4(input)):
@@ -279,6 +360,20 @@ def test_color_hwb_4(input):
     return result
 
 
+@json_test(filename='color_hwb_4.json')
+def test_color_hwb_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    assert color.space == 'hwb'
+    (*coordinates, alpha) = color.to('srgb')
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f', {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_keywords_3(input):
     if not (color := parse_color3(input)):
@@ -310,6 +405,22 @@ def test_color_keywords_3_with_4(input):
     return result
 
 
+@json_test(filename='color_keywords_3.json')
+def test_color_keywords_3_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    elif isinstance(color, str):
+        return color
+    assert color.space == 'srgb'
+    (*coordinates, alpha) = color
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f', {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_keywords_4(input):
     if not (color := parse_color4(input)):
@@ -326,6 +437,22 @@ def test_color_keywords_4(input):
     return result
 
 
+@json_test(filename='color_keywords_4.json')
+def test_color_keywords_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    elif isinstance(color, str):
+        return color
+    assert color.space == 'srgb'
+    (*coordinates, alpha) = color
+    result = f'rgb{"a" if alpha != 1 else ""}('
+    result += f'{", ".join(_number(coordinate * 255) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f', {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_lab_4(input):
     if not (color := parse_color4(input)):
@@ -342,6 +469,22 @@ def test_color_lab_4(input):
     return result
 
 
+@json_test(filename='color_lab_4.json')
+def test_color_lab_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    elif isinstance(color, str):
+        return color
+    assert color.space == 'lab'
+    (*coordinates, alpha) = color
+    result = f'{color.space}('
+    result += f'{" ".join(_number(coordinate) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f' / {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_oklab_4(input):
     if not (color := parse_color4(input)):
@@ -358,6 +501,22 @@ def test_color_oklab_4(input):
     return result
 
 
+@json_test(filename='color_oklab_4.json')
+def test_color_oklab_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    elif isinstance(color, str):
+        return color
+    assert color.space == 'oklab'
+    (*coordinates, alpha) = color
+    result = f'{color.space}('
+    result += f'{" ".join(_number(coordinate) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f' / {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_lch_4(input):
     if not (color := parse_color4(input)):
@@ -374,6 +533,22 @@ def test_color_lch_4(input):
     return result
 
 
+@json_test(filename='color_lch_4.json')
+def test_color_lch_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    elif isinstance(color, str):
+        return color
+    assert color.space == 'lch'
+    (*coordinates, alpha) = color
+    result = f'{color.space}('
+    result += f'{" ".join(_number(coordinate) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f' / {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_color_oklch_4(input):
     if not (color := parse_color4(input)):
@@ -390,6 +565,22 @@ def test_color_oklch_4(input):
     return result
 
 
+@json_test(filename='color_oklch_4.json')
+def test_color_oklch_4_with_5(input):
+    if not (color := parse_color5(input)):
+        return None
+    elif isinstance(color, str):
+        return color
+    assert color.space == 'oklch'
+    (*coordinates, alpha) = color
+    result = f'{color.space}('
+    result += f'{" ".join(_number(coordinate) for coordinate in coordinates)}'
+    if alpha != 1:
+        result += f' / {_number(alpha)}'
+    result += ')'
+    return result
+
+
 @json_test()
 def test_stylesheet_bytes(kwargs):
     kwargs['css_bytes'] = kwargs['css_bytes'].encode('latin1')
diff --git a/tinycss2/color4.py b/tinycss2/color4.py
index 4c78f1a..dd4508e 100644
--- a/tinycss2/color4.py
+++ b/tinycss2/color4.py
@@ -23,8 +23,11 @@ class Color:
     to [0, 1]. Coordinates can also be set to ``None`` when undefined.
 
     """
+    COLOR_SPACES = COLOR_SPACES
+
     def __init__(self, space, coordinates, alpha):
-        assert space in COLOR_SPACES, f"{space} is not a supported color space"
+        if self.COLOR_SPACES:
+            assert space in self.COLOR_SPACES, f"{space} is not a supported color space"
         self.space = space
         self.coordinates = tuple(
             None if coordinate is None else float(coordinate)
diff --git a/tinycss2/color5.py b/tinycss2/color5.py
new file mode 100644
index 0000000..823fba5
--- /dev/null
+++ b/tinycss2/color5.py
@@ -0,0 +1,115 @@
+from . import color4
+
+COLOR_SPACES = color4.COLOR_SPACES | {'device-cmyk'}
+COLOR_SCHEMES = {'light', 'dark'}
+D50 = color4.D50
+D65 = color4.D65
+
+
+class Color(color4.Color):
+    COLOR_SPACES = None
+
+
+def parse_color(input, color_schemes=None):
+    color = color4.parse_color(input)
+
+    if color:
+        return color
+
+    if color_schemes is None or color_schemes == 'normal':
+        color_scheme = 'light'
+    else:
+        for color_scheme in color_schemes:
+            if color_scheme in COLOR_SCHEMES:
+                break
+        else:
+            color_scheme = 'light'
+
+    if isinstance(input, str):
+        token = color4.parse_one_component_value(input, skip_comments=True)
+    else:
+        token = input
+
+    if token.type == 'function':
+        tokens = [
+            token for token in token.arguments
+            if token.type not in ('whitespace', 'comment')]
+        name = token.lower_name
+        alpha = []
+
+        if name == 'color':
+            space, *tokens = tokens
+
+        old_syntax = all(token == ',' for token in tokens[1::2])
+        if old_syntax:
+            tokens = tokens[::2]
+        else:
+            for index, token in enumerate(tokens):
+                if token == '/':
+                    alpha = tokens[index + 1:]
+                    tokens = tokens[:index]
+                    break
+
+        if name == 'device-cmyk':
+            return _parse_device_cmyk(tokens, color4._parse_alpha(alpha), old_syntax)
+        elif name == 'color':
+            return _parse_color(space, tokens, color4._parse_alpha(alpha))
+        elif name == 'light-dark':
+            return _parse_light_dark(tokens, color_scheme)
+        else:
+            return
+
+
+def _parse_device_cmyk(args, alpha, old_syntax):
+    """Parse a list of CMYK channels.
+
+    If args is a list of 4 NUMBER or PERCENTAGE tokens, return
+    device-cmyk :class:`Color`. Otherwise, return None.
+
+    Input C, M, Y, K ranges are [0, 1], output are [0, 1].
+
+    """
+    if old_syntax:
+        if color4._types(args) != {'number'}:
+            return
+    else:
+        if not color4._types(args) <= {'number', 'percentage'}:
+            return
+    if len(args) != 4:
+        return
+    cmyk = [
+        arg.value if arg.type == 'number' else
+        arg.value / 100 if arg.type == 'percentage' else None
+        for arg in args]
+    cmyk = [max(0., min(1., float(channel))) for channel in cmyk]
+    return Color('device-cmyk', cmyk, alpha)
+
+
+def _parse_light_dark(args, color_scheme):
+    colors = []
+    for arg in args:
+        if color := parse_color(arg, color_scheme):
+            colors.append(color)
+    if len(colors) == 2:
+        if color_scheme == 'light':
+            return colors[0]
+        else:
+            return colors[1]
+    return
+
+
+def _parse_color(space, args, alpha):
+    """Parse a color space name list of coordinates.
+
+    Ranges are [0, 1].
+
+    """
+    if not color4._types(args) <= {'number', 'percentage'}:
+        return
+    if space.type != 'ident' or not space.value.startswith('--'):
+        return
+    coordinates = [
+        arg.value if arg.type == 'number' else
+        arg.value / 100 if arg.type == 'percentage' else None
+        for arg in args]
+    return Color(space.value, coordinates, alpha)