MTG Salvation

If that's accurate, then these colors are pretty easy slots to start with, especially as they typically try to tie the Commander products into recent themes/sets in order to allow easy access to cards to modify the decks (think of the recent vampires deck releasing near Ixalan). I expect the decks to be two or three color, but if there are three color decks, then the main pair is likely easier to call.

madness - This is a pretty easy RB, especially after the last innistrad. Green has historically had some place in madness decks, while U for looting/wonder could work well as well. RUB can tie well into reanimation themes on top of the madness/discard, with things like Sedris, the Traitor King. Since the recent RB madness has been themed with vampires, a white splash could fit here for the Ixalan support.
My guess: BR

flashback - Flashback as referenced on cards has usually been UB - thrink Wrexial, the risen deep or Dralnu, Lich Lord - however R has often had a lot more support in color. Kess, Dissident Mage is a recent print that falls right into these colors.
My guess: UB, possibly red - but having two decks share RB seems odd. Especially since the themes are so similar.

morph - Morphs are in every color, but Morph support has typically been UG (Secret plans). Blue has some of the more popular and powerful morphs, followed closely by green, but this is a bit harder to pin colors on. Red would give an oppurtunity to toss Akroma in, because that's always funny.
My guess: UG.

populate - WG - wg has always been the populate colors, but as far as token support goes, I'd love to see some U added in here as well. Blue has much better token (copy) creation, which is far more interesting to populate. That said, white and green have some decent token copy support, especially with abilities like eternalize.
My guess: WG maybe a third color.

Red and White are underrepresented in those color pairs.

I like that they explore design space and ideas, so to that end I don't mind commanders that have a bit of an emblem attached. It gives you another unique way to build your deck and play the game. I do feel that some of them have been a bit stronger than I'd like though.