[css-color-4] export definition of valid color

Author: svgeesus

css-color-4/Overview.bs

@@ -2937,6 +2937,8 @@ Profiled, Device-dependent Colors</h2>
 	Each argument represents either an <dfn export>invalid color</dfn>, as described below,
 	or a [=valid color=].
 
+	Any color which is not an [=invalid color=] is a <dfn export>valid color</dfn>.
+
 	A color may be a [=valid color=]
 	but still be outside the range of colors
 	that can be produced by an output device
@@ -2946,7 +2948,7 @@ Profiled, Device-dependent Colors</h2>
 
 	An out of gamut color has component values
 	less than 0 or 0%, or greater than 1 or 100%.
-	These are are not invalid; instead, they are
+	These are are not invalid; instead, for display, they are
 	<a>gamut-mapped</a> using a relative colorimetric intent
 	which brings the values within the range 0/0% to 1/100%
 	at computed-value time.