So, since not all of the planets get scanned, or are even accessible via portal, it wouldn’t be super useful to write something to go through all scanned worlds on the API to determine color frequency.
I occasionally do color scans of worlds I am aware of and compile color frequency into a static page I post. My last scan was on Oct 31, but there is a link to it here: Sov Planet Scan Data
It’s not likely to be up to date, since that was 2 months ago, but it’s the best resource for what you are looking for, imo.