This effect is quite popular on forums, its not just as easy as taking the colour away....
1. Open your eye (click image for higher quality version to start with)
2. Desaturate (take out the colour) , by clicking Image > Adjustments > Desaturate
3. This doesn't look bad... but lets make it better by clicking Image > Adjustments > Levels - the following settings work for THIS image. For different images, you may have to slightly adjust the settings.
5. Now, grab the circular marquee tool (right click the rectangular marquee tool) and select the pupil. There is gonna bee too much of the pupil selected though...
6. So... use the "intersect with selection" tool, (found on the image above) by clicking the last of the four buttons at the top of the screen when the marquee tool is selected. Now, drag from the bottom right of the eye, and drag up so your including the bits you want to keep of your selection.
7. This will leave you just selected with your pupil. Now, hold CTRL and press U (to colorize it)Check the colorize box, put the saturation up to about 50 and play about with the Hue ---->
Add a few extra features, make it into an avatar or a signature!
More Tutorials: 
