The answer is, use coloured mounts!
I prefer a coloured mount with a white insert if working on white paper or board. If you are using a coloured paper, repeat that colour as an insert inside your main mount. Always double mat(board) your work. It looks much better than a single mount.
For a frame, I often use a simple, matte black moulding; elegance without being too obvious.
Greyscale drawings can be dull and unexciting. Good framing will do wonders to any artwork.