[css-color-4][editorial] Update changes

Author: svgeesus

css-color-4/Overview.bs

@@ -5672,6 +5672,28 @@ parsing/color-valid.html
 <h2 id='changes' class='no-num'>
 Changes</h2>
 
+<h3 id="changes-from-20211215">Changes since the
+	<a href="https://www.w3.org/TR/2021/WD-css-color-4-20211215/">Working Draft of 15 December 2021</a>
+</h3>
+
+<ul>
+	<!-- To 05 Feb 2022 -->
+	<li>Avoided an infinite loop in gamut reduction, with colors whiter than white or darker than black</li>
+	<li>Clarified serialization of the ''none'' value</li>
+	<li>Clarified the opt-in to interpolation in OKLab, for non-legacy colors</li>
+	<li>Defined how premultiplication works, with the ''none'' value</li>
+	<li>Clarified that missing values in rgb serialize as 0</li>
+	<li>Clarified the use of calc() with the ''none'' value</li>
+	<li>Typo, inconsistent casing on System Colors</li>
+	<li>Added example of SelectedItem with SelectedItemText</li>
+	<li>Explicitly noted the presence or absence of legacy colors</li>
+	<li>Added normative reference for CIE XYZ</li>
+	<li>Added normative reference for HWB and HSL</li>
+	<li>Clarified that ''hwb()'' is not a legacy syntax so does not support the older, comma-separated syntactic form</li>
+	<li>Clarified that only legacy colors will gamut map, the others are unbounded</li>
+	<li>Use distinct terms, spectrophotometer and spectroradiometer</li>
+</ul>
+
 <h3 id="changes-from-20210601" class="no-num">Changes since the
 	<a href="https://www.w3.org/TR/2021/WD-css-color-4-20210601/">Working Draft of 1 June 2021</a>
 </h3>
@@ -5955,6 +5977,8 @@ Changes from Colors 3</h3>
 		<li>All uses of <<alpha-value>> now accept <<percentage>> as well as <<number>>.
 
 		<li>4 and 8-digit hex colors have been added, to specify transparency.
+
+		<li>The ''none'' value has been added, to represent powerless components.
 	</ol>