[css-color-4] update default style rules, fix w3c#4863

Author: svgeesus

css-color-4/Overview.bs

@@ -953,11 +953,11 @@ System Colors</h3>
 		<dt><dfn>CanvasText</dfn>
 		<dd><span class="swatch" style="--color: canvastext"></span>&nbsp;Text in application content or documents.
 		<dt><dfn>LinkText</dfn>
-		<dd><span class="swatch" style="--color: linktext"></span>&nbsp;Text in non-active, non-visited links.
+		<dd><span class="swatch" style="--color: linktext"></span>&nbsp;Text in non-active, non-visited links. For light backgrounds, traditionally blue.
 		<dt><dfn>VisitedText</dfn>
-		<dd><span class="swatch" style="--color: visitedtext"></span>&nbsp;Text in visited links.
+		<dd><span class="swatch" style="--color: visitedtext"></span>&nbsp;Text in visited links. For light backgrounds, traditionally purple.
 		<dt><dfn>ActiveText</dfn>
-		<dd><span class="swatch" style="--color: activetext"></span>&nbsp;Text in active links.
+		<dd><span class="swatch" style="--color: activetext"></span>&nbsp;Text in active links. For light backgrounds, traditionally red.
 
 		<dt><dfn>ButtonFace</dfn>
 		<dd><span class="swatch" style="--color: buttonface"></span>&nbsp;The face background color for push buttons.
@@ -3187,8 +3187,9 @@ Default Style Rules</h2>
 
 	<pre class="lang-css">
 	/* traditional desktop user agent colors for hyperlinks */
-	:link { color: blue; }
-	:visited { color: purple; }
+	:link { color: LinkText; }
+	:visited { color: VisitedText; }
+	:active { color: ActiveText; }
 
 	/* a reasonable, conservative default for device-cmyk */
 	@color-profile device-cmyk {