[css-color-4] Explicitly link to CSS color 4 interpolation, for color-mix

Author: svgeesus

css-color-5/Overview.bs

@@ -239,7 +239,9 @@ Mixing Colors: the ''color-mix()'' Function {#color-mix}
 
 After normalizing both percentages, the result is produced via the following algorithm:
 
-1. Both colors are converted to the specified <<color-space>>.
+1. As described in [[css-color-4#interpolation]], 
+	both colors are converted to the specified interpolation <<color-space>>,
+	taking into account any [=analogous components=].
 2. Colors are then interpolated in the 	specified color space,
 	as described in [[css-color-4#interpolation]].
 	If the specified color space is a ''cylindrical-polar-color'' space,