The CLUT is a compression scheme where pixel values in the bitmap represent an index into a colour table where the table colours have more bits-per-pixel than the pixel values. In a system where each pixel value is eight bits, there are 256 possible values in the lookup table. This may seem a constraint but, since multiple lookup tables can be referenced, there can be many tables with varying 256 colour schemes. CLUTs work best for graphics where colours do not have to be natural.