For those of us like myself of the non-cognoscente, -snapview RGB is fine when starting mess.exe with command line options. If you are using QMC2 or messui.exe, you won't be able to use a command line option so alter the ini file.
# # CORE STATE/PLAYBACK OPTIONS # snapview RGB
In principle you can use QMC2 too, if you know the parameter because only "internal" as default is listed. Replace it with RGB.