[Groff] Huge fonts & colours

[M.K. Laha]

I need to do some posters and I wish to do them in groff.
Using groff, is it possible to:

  a. Print characters in font sizes greater than 36?
  b. Print selected portions of lines or paragraphs in colour
     (on a colour injet)?

I shall be obliged to get any tips/pointers/HOWTOs (or even an
authoritative answer saying NO!).

Thanks in anticipation.

- Manas Laha