The thing to rememeber is it's not an "ICON" but a simple image in PNG format. Most photo software applications have an adjustment operation that will do something basic like this. You will just need the abilty to save it out as a PNG again.

Look for "color Adjustment" or "HUE" or something like that. Even the simple software that comes with todays digital cameras usually have the abilty to "Adjust" the image.