As for skin tone, I don't think that medieval europe had quite a lot of that. Different skin tones were in foreign lands. At which point any case of killing was killing different skin tones.
You're wrong. It was pretty widespread inside medieval Europe too. Jews were often identified by skin tone, and it wasn't that unusual for them to be massacred wholesale. See, for example, the Clifford's Tower massacre in York:
http://www.historyofyork.org.uk/themes/norman/the-1190-massacre.
There's also the gypsies/roma who migrated to Europe during the Middles Ages and have been persecuted ever since (often being identified by their skin tone:
http://euroheritage.net/gypsieshistory.shtml).
I know that's getting away from the main point of this thread, but I thought it was good to point it out.
