Oda coloured the throne red on the cover of volume 90. Which was right there in Redon's post with all the download links. A little hard to miss.
In cases without Oda's art to compare with, the only real measure of what hasn't come out and intended is if it was altered for the Vivre Cards, which to my knowledge has only happened with Morgan, Helmeppo's original outfit and Vitan. Out of thousands of characters, the colour manga's track record is pretty damn good. I'd defer to it over the anime for colour accuracy.
(This is of course excusing cases where Oda himself has flip-flopped, so, Kuma's orange/blue clothes, Law's blue/black hair and Franky's blue/black Wano outfit, where the colour manga had to pick one side or the other)
Gosh, I missed the cover. My bad. I knew they kept track of A LOT of characters, even ones like Pearl that kept the original colours instead of the anime's. It's a shame that they changed Kuma's colour in his first appearance (it could have counted as a different outfit to me), but I understand that Oda changed the colours cause he liked the blue one better.
The fact that you can count only three characters talks about how much they care about this.