I am in a ‘mixed race’ marriage (my wife is creole). We have noticed over the years that it is only the ‘liberals’ with whom we come in contact who ever mention our differences. The conservatives we know (many of them) have never made even casual mention of it. The libs are always surprised at her very strong right of center politics, they think she must have been brain-washed (somebody actually said that). That is because libs see categories and conservatives see people.
Plus, they are the most color-obsessed people on earth, the group-think habit you mention is probably why.
As I posted yesterday, the typical liberal finds racial overtones in the labels of Johnnie Walker Scotch.