colormap=rgbmap(c_1,c_2,...,c_n,N,opt,graph);

input:
c_1,c_2,...,c_n - color variables: vectors, matrix(nx3) or strings (if 'rgb' function is available)
N - colormap length (default N=64)
opt='natural' (default) or 'fixed' - various approaches for color interpolation:
%for example, see the difference comparing >>rgbmap(bone,jet,'fixed','graph'); and >>rgbmap(bone,jet,'graph');
graph=<none>(default) or 'graph' or 'graph3' - last two options represent the colormap in 2D and 3D