Problems setting colours when exporting animated gifs

[Toby from Shape]

I have a simple After Effects created animated gif that should work in 8 colours. The predominant colours are red and white. 

I'm re-exporting the gif from Photoshop as After Effects has disappointingly limited output options for animated gifs

When I set the colours to adaptive, or any of the options available (including custom), what should be white (it's one of the two dominant flat colours) is #fbfbfb, which doesn't make much sense.

If I try to change the colour (in the 'save for web' dialogue by clicking the color and double clickng the swatch), it changes in the colour dialouge, but when I reopen the swatch to check it's gone back to #fbfbfb. 

This renders the gif useless as it needs to appear on a white background. 

I have tried many configurations in the dialogue.

Also, loading the gif back in loads as RGB and not indexed colour, so there seems to be no option outside of the save for web dialogue available to me to change the colour in a sceond pass. 

I've had some limited lucky success with multiple tries but I've not found a reliable way around this

Also, there's some buttons under the swatch library, and these seem to work erratically or not at all. 

I'm using cc 20.0.1 on Mojave 10.14.4

[Chuck Uebele]

I tried it, and could not reproduce what you're getting, but you said that you have had limited success. As far as the gif loading as RGB rather than index color, index color can't support layers, which the animated gif needs. I know it's a stock answer, but have you tried resetting your preferences?