Well it depends on the media. Though the G1 Frenzy toy is blue, there is no denying that he is red in the English cartoon. It honestly doesn't matter, and most media that draw inspiration from either the cartoon or comic or toyline should reflect the one they draw on the most.
For example, if a new animated movie was based mostly off the aesthetics and everything of the G1 cartoon, then Rumble should be blue and Frenzy red. If the relation is relatively loose and the designs/concepts of the new media have little to do with a particular incarnation of old, then you'd probably make Rumble red for sake of consistency.
Seeking the Following:
- CW Brawl
- Earthrise Runabout
- Earthrise Thrust