Not exactly extremely colorful unless one is discussing chakra stones (a series of gem stones placed on the chakras during a hot stone massage).
Although I have heard of some MTs using marble cold stones for contrast during a hot stone massage, especially on the face to "tone"...
There are also crystal facial massages that feature various colored crystals applied to the face.
I think I've heard of Jade stones also being used, and it is known to come in various colors (green, purple, yellow, red and black to my knowledge). Though this may also be used in the application of cold for contrast during a hot stone massage, I've never known anybody that had them.
Although, I will mention that that basalt stones my employer purchased from Massage Warehouse do have a few stones with a greenish cast.
And the basalt stones I received while taking my Gaia's Touch Hot Stone Continuing Education Course... well some of them are a bit reddish or pinkish in color.
The reason for the variation in the black basalt stones having slightly different hues is because of the additional mineral content in that area of the earth where these stones were formed.
The Columbia Encyclopedia, 6th ed., says "basalt , fine-grained rock of volcanic origin, dark gray, dark green, brown, reddish, or black in color."
So there would be some color variation even among basalt stones alone.
Hot stone massages can be fun! And your stones can be collected from places all over the world. That to me, makes each service special.