Yes Barb.
They appear as a standard set of "3 dot" sights till lowering lighting levels allow them to be seen over ambient light. Fortunately, the point of ambient lighting where we lose our regular sights, is where the Tritium becomes visible.
My understanding is that selection of colors other than the standard green, shortens life span of the gas in the vials. Till relatively recently, they were only available in green. They're now available in yellow, orange, blue, red but with the penalty of shorter life and lower brightness. My guess is, that some type of phosphor must be installed in the vial to change it's color and that addition or the shorting of the Tritium affects the life span?
And Gator has hit my hot button soap box subject! PLEASE Tru-Glo! Start making the combination fiber optic/Tritium sights for S&W products, not just Glocks! They're the best of both worlds!