Add 'none' components to color(). #6107

Author: tabatkins

css-color-4/Overview.bs

@@ -3371,7 +3371,7 @@ Profiled, Device-dependent Colors</h2>
 	Its syntax is:
 
 	<pre class='prod'>
-		<dfn>color()</dfn> = color( [<<ident>> | <<dashed-ident>>] [ [ <<number-percentage>> | none]+ ] [ / <<alpha-value>> ]? )
+		<dfn>color()</dfn> = color( [<<ident>> | <<dashed-ident>>] [<<number-percentage>> | none]+ [ / [<<alpha-value>> | none] ]? )
 	</pre>
 
 	<!-- check this test, remove any fallback testing -->