I put Truglo sights on my XD. The SA rep said the XDm uses the same Truglo as the XD. The sights are fiber optic by day, and the tritium lights the fibers by night. Sights cannot be seen by the target. I'm extremely happy with these sights.

I've seen green front/green rear for $79.99 (Natchez Shooters Supply, I think) and the green front/yellow rear for a little over $100 at Optics Planet.
I bought the green/yellow as the rear yellow sights are a bit dimmer than the green front, lets me differentiate between dots in low light much quicker.
http://www.truglo.com/IW_Products.m4p.pvx?;PRODUCTS_NO_TREE?cat=30500?company=TGIClick on brite site series TFO, you want the tg131xt for green/green, or the tg131xty for yellow/green