Hi Fallen Son, welcome to the community. We hope you enjoy your stay.
As to your question, it's actually quite a simple solution.
First choose a new colour. Add a new layer above your photo. Grab a soft brush and hold it over one of the eyes. Tap the [ key to reduce the brush size or the ] key to increase it, until the brush is the same size as the iris. Then click then brush once over each iris.
Now change the Blend Mode to Color/Overlay/Softlight/Hardlight... which ever suite your taste. Reduce Opacity if need be.
TIP: you can now opne the HUE&SAT filter and change the HUE of the colour in realtime, until you get the one you like best. [righton]
HINT: there are a few other methods around, but they usually involve destructive editing -- which i hate. This method allows the original photo to remain untouched.