[css-color-4] Add XYZ examples for white (D65 has Z greater than 1)

Author: svgeesus

css-color-4/Overview.bs

@@ -4328,6 +4328,16 @@ The Predefined CIE XYZ Color Spaces: the ''xyz-d50'', ''xyz-d65'', and ''xyz'' k
 					</pre>
 				</div>
 
+				<div class="example" id="ex-xyz-white">
+					These colors are exactly equivalent, and represent white:
+
+					<pre class="lang-css">
+						<span class="swatch" style="--color: #FFFFFF"></span> #FFFFFF
+						<span class="swatch" style="--color: ##FFFFFF"></span> color(xyz-d50 0.9643 1 0.8251)
+						<span class="swatch" style="--color: ##FFFFFF"></span> color(xyz-d65 0.9505 1 1.089)
+					</pre>
+				</div>
+
 	</dl>
 	<wpt>
 		predefined-016.html