Other than a change of gimmicks and physical appearance (i.e. Deluxe Galvatron), Hasbro generally keeps a familiar color scheme for the Generations toys. It may not always be perfect or completely accurate, but I can't think of a Generations toy that looks completely different in color scheme to how they should do. A quick l;ook around my room and I can't see anyone who is completely the wrong color scheme. I'd say the FoC Combaticons and Wreckers are the wrong colors, but they're not supposed to be the G1 characters so they get a pass.
And yet the comics are not damned. This is G1 Sentinel Prime, not Animated or Movie Sentinel Prime and so he should look the part to how G1 Sentinel Prime has been portrayed so far. An Animated Sentinel Prime color scheme can come later. I don't recall how important the G1 legacy of Primes (Convoys) is in Japan or even if they have Nova Prime, Sentinel Prime, and previous Primes. So maybe Takara will paint him as Animated Sentinel just because its what Japanese fans are most familiar with. Sentinel Prime didn't have to have been a pre-use of the Astrotrain mold, indeed why even choose G1 Sentinel Prime at all after how long neglecting him?
Regarding MTMTE#55 being released early in some places, its okay to discuss the contents of the issue as long as spoilers are kept within the thread. I refuse to read discussion threads of comics I have yet to read to avoid being spoiled. I also find it pointless to go into a discussion thread and expect to not be spoiled if you have yet to read the issue (unless you don't care).