We currently have RGB and HSV palette definition, and linecolor now accepts rgbalpha data (see https://sourceforge.net/tracker/?func=detail&aid=3249698&group_id=2055&atid=352055\). Why can't we have palette definitions that incorporate alpha, too, such as
set palette RGBA grey,grey,grey,1-grey
set palette HSVA grey,1,1,1-grey
This would be helpful, especially in overlaying a pm3d surface over another surface beneath it to display multivariate data; for example, in showing a cloud surface.