Use the 'transparent black' and 'opaque black' terms.

Author: tabatkins

css-color-4/Overview.bs

@@ -724,10 +724,7 @@ For historical reasons, this is also referred to as the X11 color set.
 <h3 id='transparent-color'>
 The ''transparent'' keyword</h3>
 
-	The keyword <dfn value for="<color>">transparent</dfn> specifies a transparent black color;
-	that is, a color with its red, green, and blue channels all set to the minimum value
-	and its alpha channel set to full transparency,
-	equivalent to ''rgb(0 0 0 / 0)''.
+	The keyword <dfn value for="<color>">transparent</dfn> specifies a <a>transparent black</a>.
 	It is a type of <<named-color>>.
 
 
@@ -1904,8 +1901,7 @@ Profiled, Device-dependent Colors</h2>
 	specified by the first of its arguments that represent a <dfn export>valid color</dfn>
 	(that is, the first argument that isn't an <dfn export>invalid color</dfn>).
 	If all of its arguments represent <a>invalid colors</a>,
-	''color()'' represents a fully opaque black,
-	identical to ''rgb(0 0 0)''.
+	''color()'' represents <a>opaque black</a>.
 
 <h3 id="predefined">
 Predefined colorspaces: ''srgb'', ''image-p3'', and ''rec2020''.</h3>