Can I have two-tone, 3D characters on my number plate?

If it's before September 2021, then the answer to this question is yes.

If not, it's no.

As of September 2021, two-tone digits are longer be allowed on UK number plates due to stricter definitions of black from the DVLA, and the need to have a clear distinction between the digit and retro-reflective NIR values. This is to assist ANPR cameras pick up your reg.

This change comes about because of shift to a new British Standard (BS145e), enforced from September 2021.