start adding color-contrast section

Author: svgeesus

css-color-5/Overview.bs

@@ -11,6 +11,7 @@ Editor: Chris Lilley, W3C, chris@w3.org, w3cid 1438
 Editor: Una Kravets, Google
 Editor: Lea Verou, Invited Expert, http://lea.verou.me/about, w3cid 52258
 Abstract: This module extends CSS Color [[css-color-4]] to add color modification functions.
+Repository: w3c/csswg-drafts
 </pre>
 
 Introduction {#intro}
@@ -79,24 +80,39 @@ a plain number or percentage can be specified,
 which applies to all color channels.
 
 <div class="example">
-		This example produces the mixture of red and yellow,
-		in ''lch'' colorspace (the default),
-		with each lch channel being 65% of the value for red
-		and 35% of the value for yellow.
-
-		Note: interpolating on hue and chroma
-		keeps the intermediate colors
-		as saturated as the endpoint colors.
-
-		<pre class="lang-css">mix-color(red, yellow, 65%);</pre>
-
-		The calculation is as follows:
-		  * sRGB red (#F00) is lch(54.2917 106.8390 40.8526)
-		  * sRGB yellow (#FF0) is lch(97.6071 94.7077 99.5746)
-		  * mix lightness is 54.2917 * 0.65 + 97.6071 * 0.35 = 69.4521
-		  * mix chroma is 106.83 * 0.65 + 94.7077 * 0.35 = 102.5872
-		  * mix hue is 40.8526 * 0.65 + 99.5746 * 0.35 = 61.4053
-		  * mixed result is lch(69.4521 102.5872 61.4053)
-		  * which is a red-orange: rgb(75.3600% 65.6304% 16.9796%)
+	This example produces the mixture of red and yellow,
+	in ''lch'' colorspace (the default),
+	with each lch channel being 65% of the value for red
+	and 35% of the value for yellow.
+
+	Note: interpolating on hue and chroma
+	keeps the intermediate colors
+	as saturated as the endpoint colors.
+
+	<pre class="lang-css">mix-color(red, yellow, 65%);</pre>
+
+	The calculation is as follows:
+		* sRGB red (#F00) is lch(54.2917 106.8390 40.8526)
+		* sRGB yellow (#FF0) is lch(97.6071 94.7077 99.5746)
+		* mix lightness is 54.2917 * 0.65 + 97.6071 * 0.35 = 69.4521
+		* mix chroma is 106.83 * 0.65 + 94.7077 * 0.35 = 102.5872
+		* mix hue is 40.8526 * 0.65 + 99.5746 * 0.35 = 61.4053
+		* mixed result is lch(69.4521 102.5872 61.4053)
+		* which is a red-orange: rgb(75.3600% 65.6304% 16.9796%)
+</div>
+
+Selecting the most contrasting color: the ''color-contrast()'' function {#colorcontrast}
+========================================================================================
+
+	This function takes, firstly, a single color
+	(typically a background, but not necessarily),
+	and then second, a list of two or more colors;
+	it selects from the list of colors
+	the one with highest luminance contrast
+	to the single color.
+
+	<div class="example">
+		<pre class="lang-css">color-contrast(wheat tan, sienna, var(--myAccent), #d2691e)</pre>
+
 	</div>