Kittens

As all cats are blue-eyed as kittens,[6] the differences in an odd-eyed kitten's eye color might not be noticeable save upon close inspection. Odd-eyed kittens have a different shade of blue in one eye. The color of the odd eye changes over a period of months, for example, from blue to green to yellow, until it reaches its final, adult color.

Source : http://en.wikipedia.org/wiki/Odd-eyed_cat