I wouldn't say it's racist, it honestly depends on the region a specific character exists. For instance if someone were to have story in say Nigeria or Ethiopia, you would typically expect a character to be black, while there are while people in Africa, it is a majority black nation. With England, the country is about 90% white, so most people will immediately associate an English character as white if it isn't specifically described. I don't mind people race bending or having differing interpretations of characters, it's actually quite fascinating and your art in particular is quite beautiful. I myself have always had a preference towards dark skin, mostly from how I've grown up in a fairly diverse area, and I find it quite attractive.