This could be construed as a too broad question, but some examples is all I'm asking for really. An answer based on any combination of atmosphere and star would constitute a good answer. (Or better yet, some simple way to determine what wavelength likely would be reflected by a plant in any given conditions.)
Different stars radiate different spectrums of light, and different atmospheres absorb- and scatter different amounts of different wavelengths of light.
One could assume plants would evolve to absorb the wavelengths most readily available for photosynthesis, with some wavelengths being more useful options than others, of course.
What would be the color of alien plants under some example conditions, then?
Edit: From the commments it would seem plant color is a lot more arbitrary than I gave it credit for. So I consider this pretty much answered. :)