[css-color-4] Correlated Color Temperature was used without being def…

…ined or explained. Added informative reference.

css-color-4/Overview.bs

@@ -100,6 +100,11 @@ spec: css-backgrounds-3; type: property; text: border-right-color
 			"title": "ROMM RGB",
 			"publisher": "ICC",
 			"href": "https://www.color.org/chardata/rgb/rommrgb.xalter"
+		},
+		"Understanding_CCT": {
+			"title": "What is CCT? A Guide to Choosing Correlated Color Temperature for Your Lighting",
+			"date": "2024-08-14",
+			"href": "https://litomatic.com/blog/what-is-cct-in-lighting/"
 		}
 	}
 </pre>
@@ -352,7 +357,8 @@ Value Definitions</h3>
 
 	Most color spaces use one of a few
 	daylight-simulating [=white points=],
-	which are named by the color temperature
+	which are named by the correlated color temperature (CCT)
+	[[Understanding_CCT]]
 	of the corresponding black-body radiator.
 	For example, [=D65=] is a daylight whitepoint
 	corresponding to a correlated color temperature