There is only one true answer to this age old question, which one is which? Is Frenzy red or blue? Is Rumble blue or red? The answer is clearly yes, to both questions.
If in media, it's whatever is shown. If a toy, it's what is on the freaking package. If you are talking about them in reference to any of these, stick to what it's stated as and keep your personal preference to appropriate threads instead of starting the stale and annoying debate that's been done thousands of times already. People need to get over this, it's one of the most annoying rant of the fandom.
Official? Rumble is red, Frenzy is blue. Cartoon? Reversed. Your choice? Entirely up to you. Don't piss all over someone else's opinion and they won't on your's, simple as that.
Both can be correct, but I grew up with the G1 show…so Rumble has always been blue for me. I think someone added up all the different iterations recently and determined that Rumble is actually the red one in most instances.
In my brain Rumble will always be blue because of the G1 cartoon. If you tell me otherwise because of numerous toys or comics, it would still be the like telling me Lazerbeak is yellow and Buzzsaw is red.
I say Rumble is this way, because of this supporting evidence, which is better than your supporting evidence for your position. Yeah, I know it doesn't really matter, and you can enjoy Rumble however you prefer, as long as you know that I'm the one who's RIGHT ABOUT THIS. YOU HEAR ME!!?
A silly, personal headcanon of mine has always been that they swap colors often. You can't seriously tell me those little gremlins wouldn't.
We are in dire need of a multiverse story in which Rumble meets himself and mistakes himself for Frenzy.