Color coded lookup values.

OOTB Lookups such as "Contact Type" and "Account Type" have the column "Colour", which is used to allow the lookup on a list to be colour coded. 

I have tried adding a "UsrColor" to custom objects/lookups, but the functionality does not seem to work. I also can't see any baselookup where this column is already there. 

Has anyone else managed to do this?