[css-color-5] Serialization of specified value of color-mix

Author: svgeesus

css-color-5/Overview.bs

@@ -2586,6 +2586,21 @@ an implicit value of 1 (fully opaque) is the default.
 	Serializing color-mix()
 </h3>
 
+The serialization of the specified value of a ''color-mix()'' function
+is the string "color-mix(in ",
+followed by the specified <<color-space>> in all-lowercase,
+followed by ", ",
+followed by the first specified color,
+followed by a space,
+followed by the normalized first percentage,
+followed by ", ",
+followed by the second specified color,
+followed by ")".
+
+Following the principle of shortest serialization,
+and given that the normalized percentages are serialized,
+the normalized second percentage is omitted.
+
 The serialization of the result of a ''color-mix()'' function
 is a <<color>>,
 as defined in [[css-color-4#serializing-color-values]].