This command graphically tests or presents terminal and palette capabilities.
Syntax:
test {terminal | palette [rgb|rbg|grb|gbr|brg|bgr]}
test or terminal creates a display of line and point styles and other useful things appropriate for and supported by the terminal you are just using.
palette draws graphically profiles R(z),G(z),B(z), where 0<=z<=1, as calculated by the current color palette. In other words, it is a beautiful plot you would have to construct from the result of `show palette palette 256 float`. The optional parameter, a permutation of letters rgb, determines the sequence of r,g,b profiles drawn one after the other — try this yourself for `set palette gray`. The default sequence is rgb.