Nah. It's not, or wasn't, Redshift. Nor is it a vision issue. I can have the emoji picker on screen at the same time as my comment and they're definitely very different colours.

I think the picker uses images, but the on-screen text renderer in Firefox is using the Noto Color Emoji font as a substitution (because the text font doesn't have emojis) and whatever Firefox has set as the default colours for the glyphs in it.

My picker clearly doesn't know how to generate the right modifier sequences to change those, and I don't think it's worth mucking around with Unicode zero-width joiners and colour modifiers to try to figure it out.