2M Series styli interchangeability:
The 2M Series' engines, coils and magnets configurations are not identical: Red and Blue are identical, so are the Bronze and Black and so are the true mono variants 2M Mono and 2M 78. Likewise, 2M series styli are interchangeable within the below combinations: 
- 2M Red, 2M Blue and 2M Silver
- 2M Bronze and 2M Black
- 2M Mono and 2M 78

Compatibility with Rega brand TT/TA: 
REGA brand cartridges’ height from stylus tip to the top cartridge mounting surface is lower than standard. Therefore you would need spacers to ensure the correct set-up of the Ortofon cartridge. . 
Adjusting the height of your Rega tonearm is easy with Acoustic Signature's Spacer Set. It allows you to adjust the height from 0.5 mm to 3.5 mm in precise steps of 0.5 mm - without removing the tone arm. Simply loosen the screws, insert the AS-spacer, then lock the screws back down, and you're tonearm is ready to play.
3.2 - 4 mm spacers should be enough for 2M cartridge.