Definition:
A palette is the surface on which an artist lays out their colors (paints) as well as the range of colors an artist works with (see for instance Basic Color Palette for Acrylics).
Palettes can be wood, plastic, or a disposable palette where you simply tear off the top sheet from a pad of paper and throw it away when you're finished painting. Special palettes are available for acrylic painting to stop the paint drying out too fast – the paint sits on a sheet of wax paper place on top of a damp piece of watercolor paper.
See also:
