Before:
And After:
The process:
Select your eyes with a mask and have it into it's own layer.
In layer type select "colour", then select the contents of the layer and with the paint bucket tool (and with the colour you want already selected) click on your two eyes.
Then reduce the opacity of this layer to strengthen or weaken the effect, noting that the stronger it is, often the more fake it looks.
Interesting with black and white as well:
