Terms searched for were combinations of eye colour, mismatch, variation, terms, colloquialism, slang (checked out mosaicism but no colloquialisms there!)
ETA: thanks to all for heterochromia, but "that heterochromic bastard" doesn't have the right ring somehow! For further information, I have unbounded admiration for Anastasius, but my character detests him because he started off his reign (in fact, it was a major factor in his being made Emperor) as apparently Orthodox but has recently been emerging as a Monophysite. And this is, after all, the Eastern Empire in the late 5th century.
