If you wonder about linux: gcolor2 (http://gcolor2.sourceforge.net/) does the job.
And for size fetishists: it weights 42KB.
And for size fetishists: it weights 42KB.
Maybe.
It looks like it's been spun out into `x11-apps` on debian based distros in the last year or two, and for some reason I don't have that package installed despite using X
And the EXE is only 32 KB when UPX is applied on it. And uses only 1 MB of RAM when running.