[css-color-4] clarifications

Author: svgeesus

css-color-4/Overview.bs

@@ -2363,8 +2363,8 @@ Converting predefined colorspaces to Lab</h4>
 	<ol>
 		<li>Convert from gamma-corrected RGB to linear-light RGB (undo gamma encoding)
 		<li>Convert from linear RGB to CIE XYZ
-		<li>Convert from a D65 whitepoint (used by both display-p3 and rec2020) to the D50 whitepoint used in Lab,
-			with the Bradford transform
+		<li>Convert from a D65 whitepoint (used by sRGB, ''display-p3''', ''a98-rgb''' and ''rec2020''') to the D50 whitepoint used in Lab,
+			with the Bradford transform. ''prophoto-rgb''' already has a D50 whitepoint.
 		<li>Convert D50-adapted XYZ to Lab
 	</ol>
 
@@ -2377,15 +2377,15 @@ Converting Lab to predefined colorspaces</h4>
 
 	<ol>
 		<li>Convert Lab to (D50-adapted) XYZ
-		<li>Convert from a D50 whitepoint (used by Lab) to the D65 whitepoint used in sRGB,
-			with the Bradford transform
+		<li>Convert from a D50 whitepoint (used by Lab) to the D65 whitepoint used in sRGB and most other RGB spaces,
+			with the Bradford transform. ''prophoto-rgb''' does not require this step.
 		<li>Convert from (D65-adapted) CIE XYZ to linear RGB
 		<li>Convert from linear-light RGB to RGB (do gamma encoding)
 	</ol>
 
 	Implementations may choose to implement these steps in some other way
 	(for example, using an ICC profile with relative colorimetric rendering intent)
-	provided the results are the same for colors inside the source and destination gamuts.
+	provided the results are the same for colors inside both the source and destination gamuts.
 
 <h3 id="at-profile">
 Specifying a color profile: the ''@color-profile'' at-rule</h3>