[Break Change] Adjust the color palette

[sainnhe]

The background colors have been adjusted since #108 and #109.

If you ported this color scheme to other apps, you should consider updating the colors.

[talwat]

I feel like if you want people to update their apps, it's probably now the best time to document all the colors in the README, which would make porting everything miles easier.

[talwat]

https://github.com/sainnhe/everforest/pull/92