[css-color] Make definition of resolving color values match implementations better

Author: frivoal

css-color/Overview.bs

@@ -190,15 +190,18 @@ Resolving Color values</h2>
 		The computed value and used value of
 		<a>named colors</a> (including <<deprecated-system-color>> colors),
 		3 and 6 digits <a>hex colors</a>,
+		4 and 8 digits <a>hex colors</a> with an explicitly opaque alpha channel,
 		comma separated ''rgb()'' colors without an alpha channel,
-		and comma separated ''hsl()'' colors without an alpha channel,
+		comma separated ''rgba()'' colors with an explicitly opaque alpha channel,
+		comma separated ''hsl()'' colors without an alpha channel,
+		and comma separated ''hsla()'' colors with an explicitly opaque alpha channel,
 		is the equivalent numeric value in comma separated ''rgb()'' notation omitting the alpha value.
 
 		<li>
 		The computed value and used value of
-		4 and 8 digits <a>hex colors</a>,
-		comma separated ''rgba()'' colors with an alpha channel,
-		and comma separated ''hsla()'' colors with an alpha channel,
+		4 and 8 digits <a>hex colors</a> with a non opaque alpha channel,
+		comma separated ''rgba()'' colors with a non opaque alpha channel,
+		and comma separated ''hsla()'' colors with a non opaque alpha channel,
 		is the equivalent numeric value in comma separated ''rgba()'' notation with the alpha value.
 
 	</ul>