I once knew a girl ( a truly beautiful natural blonde) whose eyes were partly blue and partly brown, not mixed but half one color and half the other. Actually it was two thirds blue and one third brown. I took quite a few pictures of her and her eyes really were striking.
She told me her eyes were not as uncommon as one would think as she had run into several others with the same type of eyes.
I had a grandfather with one pure blue eye, and the other one pure blue with a very well defined patch of dark brown...the brown patch was about 20% of the iris. If you looked at it just right in just the right light, it appeared he had an oblong shaped pupil.