Are fish able to see colors, other than black, white, and shades of gray?

Are all species able to see colors, or just certain ones?
Answers:
Most fish can see in color. As in people, the retina of a fish's eye contains two types of cells, rods and cones. Cones are used for day vision and are the cells used to see colors. Rods are used for night vision and cannot distinguish colors, although they can judge light intensity. The eyes of most freshwater fish contain both rods and cones, though day feeders tend to have more cones, and night feeders more rods.

In theory, then, day feeders like bass, trout, and salmon are more sensitive to color than night feeders like walleyes. Studies have shown that rainbow trout and Pacific salmon have color vision similar to that of humans. They can distinguish complementary colors and up to 24 spectral hues. Other studies have shown that brown trout are capable of sharply focusing on near and far objects at the same time and that they can clearly see different colors at different distances.

More on fish vision> http://www.seagrant.wisc.edu/greatlakesf.

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Fish have amazing color vision (much better than humans), cats and dogs are red/green color blind (they only have 2 types of cones instead of three).

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Good question, I would guess yes. Take bettas, it's recommended they not be placed with fancy fish like guppies because of their colorful fan tails. And also, for all fish, the males are usually more colorful to attract the females.
But I'm no expert :)

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Reef fish have an amazing array of colors. I'm guessing its for their benefit somehow instead of for tourists. If they were colorblind it wouldn't matter what they looked like.

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I believe so. My goldish sometimes head for things that are exactly the same colour as their food. Their precision at aiming for this exact thing is probably not coincedence.