hey guys, my first tutorial on here. Now, I don't know if this has been done before, I was just fooling around with photoshop yesturday and I found this little trick out. Be warned, I haven't found out how to do this with dark colored eyes yet, only light colored. So, here goes nothing.
Step 1: Get a picture with light colored eyes,mine just happens to be this one. Open it up in photoshop (note: this is a smaller version then what i'm actually working with.)

Step 2: Select the polygonal lasso tool (I find it easier to work with then the regular lasso tool for this project)
Step 3: Outline the iris (in case you don't know, the iris is the part of your eye where the color actually is..I think.. Lol) It helps to zoom into the eye your working on.

Step 4: Now, press ctrl+u to bring up the hue/saturation menu,check the colorize button, and then do any color you want! This was the color I used.

Step 5:This was my result.

Step 6: Now, I noticed that the edges looked kinda jagged like, So, select your blur tool! And go around the iris with the blur tool. This was my result,a bit smoother lookin now huh?

And that's mostly it. If you want, you can follow these steps again for the whites of their eyes too. This is my finaly results doing the whites of the eyes also.