> I didn't care that they were black, but my husband had never once mentioned that John was black. So I assumed he was white.

How can an assumption be racist anyway? If my friend told me about a friend I might imagine that person tall and slim with brown hair and whatever other look and if this person turns out to be short and chubby with blond hair - who cares. Obsessing about skin color like you are doing right now is completely meaningless, doesn't help anybody and just feeds the segregation even more. You can't be "subconsciously racist", don't believe those hoax psychologists that claim it.