[css-color-4] Specified values of system colors are still themselves, per #6773

Author: svgeesus

css-color-4/Overview.bs

@@ -5682,6 +5682,8 @@ Resolving values of the ''color()'' function</h3>
 	and ''color>/currentcolor''.
 
 	The specified value for each <<system-color>> keyword
+	is itself.
+	The computed value
 	is the corresponding color in its color space.
 	However, such colors must not be altered by
 	'forced colors mode'.