Personally, I would take what Glass Wolf said about the colors and the brightness and make sure you place Green at your front sight. Then either use yellow or orange to the rear. Having the brightest color at your front will help you get on sight alignment easier.
I have used Trijicon and I liked them, because they did the job they were supposed to. When I needed to replace them, I opted for the TFO's from Truglo ( Link Removed )
I went with the yellow rear sight and the green front sight for the reason mentioned above. What I love about these is that my sights don't get washed away in bright light either. In the dark, the stand out better than my Trijicons. Is this because they are brighter or because I opted for the yellow/green combination? *shrugs*