Light of any color from deep violet through the near-infrared could power photosynthesis. Around stars hotter and bluer than our sun, plants would tend to absorb blue light and could look green to yellow to red. Around cooler stars such as red dwarfs, planets receive less visible light, so plants might try to absorb as much of it as possible, making them look black.In addition to the article, which is based in solid science, there is a slide show of an artist's fantasy of what those alien plants might look like.
There are also some related informational in that issue:
Image: From the Scientific American"The Color of Plants on Other Worlds" slide show