It's the oddest of situations. Face-to-face with People of Colour, my mother is polite, cooperative, even friendly. There is no discernible difference from the way she interacts with White people. But speak about them in the abstract or in general, and it's different. "I don't mind them," she will say, "but..." and never gets round to explaining what comes after the 'but'. The closest to an explanation you get is "They're not like us." Which as I have pointed out is meaningless, because we're not like us either!
I suspect that her upbringing, largely during and after the Second World War, has left her with a feeling that societies should be homogenous and linked to shared values, customs, traditions, etc. The diversity of the present seems to disturb her on a level she can't quite articulate. My father, who is rather brighter, has adapted much better.