Artist 
Writer Spectrum palette
A large palette that consists of all the colors of the spectrum in their purest form, often with several grays (or earth colors) added in.
The full spectrum palette includes the powerful dark transparent staining pigments and has all the spectrum colors to give you the maximum flexibility in matching colors and creating color harmonies. This is the largest palette of them all, and the one I use most often, although it is the most difficult one to use and not recommended for beginners.
See the Color Building Block for more information.