check if screen uses rgb mode

[Natejoestev]

It would be nice to beable to have a check to see if the screen allows for RGB or B&W.

[pixix4]

You can already do this with the framebuffer crate, that is used internally. With screen.buffer.var_screen_info.bits_per_pixel you get 1 for black and white and 16 or 32 for screens with color support. Does this work for your usecase?