Generally Heterochromia means one eye is a different color than the other generally one dark and one light. Many "hazel" eyes have a "iris ruff" of one color and the rest of a different color. That is not an uncommon finding.
JCH MD
It could be 'central heterochromta,' in which there's a ring of one color around the pupil and a different colored ring further out. If you look carefully at eyes around you, you will see that a yellowish ring is very common, even in pale blue or grey eyes like yours.
Another form of heterochromta is 'sectoral,' in which there is not a tidy ring of color around the pupil, but splotches or blobs of a different color here and there.
Wikipedia has a great article on human eye color, with lots of cool photos. You wouldn't believe how many strange eye color variations there are!
But if you think your own color variation might be new, it wouldn't hurt to ask your eye doctor about it.