When you watch the wonder videos, the fabric colors are consistent with the leaders' "field/background" color like we have been seeing with other leaders.
For example, the Weiyang Palace clip features the Hunyadi yellow/ecru of Confucius:
The Oracle construction video features a sort of emerald green. It actually looks like the same emerald green of Hatshepsut in her reveal trailer, so I bet that's Hatty (although it does look a tad darker, maybe just the angle?). Interesting thing to note: Hatshepsut's colors have been shown both ways: emerald on sand, and sand on emerald. I'm betting there is a much simpler "jersey" system at play, where a leader's colors will simply reverse depending on whether a person they are playing against shares a background color. We have also seen her brown-on-sand, which suggests the old jersey system may be back completely.
The Angkor Wat uses a deep purple. It seems Ashoka and Augustus both use the same deep purple field/background. Probably just Ashoka playing Khmer. This does not look like the bright violet of Civ VI's Khmer.
If my hypothesis about color-reversal is true (although it may only happen occasionally), the Shawnee and Han units may have been flipped. So instead of Mayan teal-on-skyblue, it might be a flipped skyblue-on-teal, even though I think that unlikely. For the Mongolian colors, it almost doesn't matter, since Kublai and Genghis were flipped anyway; I'm still betting its Kublai since that would be his default color scheme
and he fits better with Han/Qing at launch.
ALSO, if you look at the colors of the civs shown in the twitter post for the initial batch of website civs (which are just white-on-black on the website), Aksum is Ethiopian green-on-yellow, while Amina plays Hausan white-on green (likely why China's colors got changed). While this doesn't confirm an Ethiopian leader necessarily, I do think it suggests that Amina will not lead Aksum in the final game, and it is just a placeholder for now (like Hatty and Songhai).