Metamorphic Rocks
Metamorphic rocks has a lot of colours because a lot of layers are on an existing rocks. Metamorphic rocks make up a large part of the Earth's crust and are classified by texture and by chemical and mineral. They may be made simply by being deep under the Earth's surface, caused by the high temperatures and the powerful pressure of the rock layers on top of it. Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite.
http://en.wikipedia.org/wiki/Metamorphic_rock