Grey Pikmin

The Grey Pikmin are the second-to-last type of pikmin obtained in Pikmin:Redemption and the third-to-last power obtained. You gain the power after jumping into the Smoky Candypop Bud located somewhere in the Flooded Abyss. They evolved their defining characteristic of thin skin after a large group of various Pikmin varieties were trapped in a pitch black cave for several months. This caused the skin of those pikmin to become a light grey and thinner to let in more light. Later several of the pikmin grew into Candypop Buds and then into Onions. However these Onions were not of the original pikmins' color but grey. Since the children were of mixed sub-species the Onion let any color in. This led to DNA mixing causing all future Candypop Buds from these pikmin to be randomly colored.

In Other Games
Pikmin:Shadow Planet

In Pikmin: Shadow Planet, Grey Pikmin are the 10th and last type of pikmin found. They are magnetic, so they are pulled towards treasure. ( they will stand on whatever side of your squad that is closest to treasure.) They can also dig up treasure, like whites. Unfortunately, they are sometimes pulled towards magnetic objects like certain cannon beetle boulders. They are normal looking pikmin, grey, obviously, and have four 'fingers' instead of three.

Pikmin 360

Grey Pikmin return in Pikmin 360. They are controlled by the Pikiqueen and Pikiking. It is revealed that there is also an infectious bug spread that takes control of the Pikmin and turns them grey-the grey pikmin found in this game are all infected. The Pikiking orders his grey pikmin to take control of the Pikiqueen, who later joins you with the infected pikmin. It is revealed at the end of the game that the Grey Pikmin in that contained their infection and sided with the White and Yellow colonies. It is unknown if the already-grey pikmin sided with white and yellow.