When you think of a lobster, you might think of a bright red creature, as that is what they look like when they're cooked. That's also the creature that the state of Maine had on their license plate until just a few years ago, making them the only state to have a dead animal on their license plate!
However, most lobsters are a brown to olive-green color in the wild, with only a reddish tinge. Lobsters are also occasionally unusual colors such as blue or even orange. When one of these curious creatures is caught by a lobsterman, it's usually big news, as these unusual colorations are a rarity.
Lobsters have a carotenoid pigment called astaxanthin in their shell, which provides a red coloring. However, in most lobsters, this reddish color is mixed with other colors to form the lobster's normal, often duller coloration. This coloration helps the lobster blend in well with its surroundings.
Astaxanthin is stable in heat, while the other pigments are not. This means that when a lobster is cooked, the other pigments break down, leaving only the bright red astaxanthin, thus a bright red lobster on your plate!