I think that there are a lot of plain blue-eyed blondes in England, Australia and Germany, though. Depends where the story is set. For me, plain is more indicative of being a bit meh-looking than average. I'm a brown-eyed brunette and my half-sister is a blue-eyed blonde, but she is very definitely the plainer of the two of us (and I don't say this only because I am hideously vain, though, obviously, I am ;-).)