Okay I spent hours testing and i think i finally solved it, for now. These are just notes I took.
@Josh_Smith I think that will work too.
What i did was make sure my working space in After Effects was Display P3. If you are on Mac, this is an option. On Windows you will have P3 DCI Gamma 2.6.
If your Windows monitor isnt capable of P3 viewing, you will be somewhat working in the dark. One way to find out is looking at Preferences>Color Profile in Figma. It will say if your monitor will interpret those ranges.
You can get a preview of a close match on Windows by going to view>Use Display Color Management, then simulate Apple RGB (Output Profile.) It’s not perfect, and colors wont match perfectly on non P3. If you are viewing on a non-P3 monitor then you may certainly just have to either trust this process or send to a Mac or similar P3 monitor.
H264 will always be a smaller range of colors. Quicktime, ProRes 442, 4444, etc. preserve P3 colors on export, but filesizes are massive. H264 can be close though. Color-pick the colors that stand out after exporting (preferably on a Mac or P3 monitor.)
When you export, an H264 in Media Encoder, look under video and check Mastering Display Color Volume. It should say P3D65. Lum min .0005. Lum max 1,000. CLL 1,000. Average 200. I have no idea what these mean.
Take note of this–
If you take your export from After Effects to Premiere, it seems that it will read P3 working space (it will look right in Premiere), but there is no way to export P3.
What I had to do was export my project from Premiere to After Effects and render from Media Encoder.
I still can’t see if my colors are correct on my Windows, but it seemed to work when built it on PC, and viewed the export on a Mac.
The above information could be useful. No one has commented on a solve, so I am just giving up info that can be built upon. I hope this helps and that we all have less P3 compatability nightmares. Good luck.