I just checked in Firefox beta, and yes this seems real.

This maxes out the cringe-scale. Ouff.

And I mean, they went through the massive design effort of picking a color on a color dial, then grabbing a name from Instagram. Highly Paid Brand Consulting company, I suppose.

If someone from Mozilla is reading this, stuff like this is why you don't really get taken serious as developers. This isn't stuff a professional product should do, even when trying to be playful. Nevermind that for a browser being "playful" is a questionable goal as it goes against what role the browser plays. But it you then do 13y-old-theming instead of focusing on actual themes - or even better, improve the theming engine so users can provide more meaningful themes - you'll get ridiculed.
And is it surprising? This is just pick-a-primary-color. Virtually any other browser just allows the user to select a color from a wheel, Vivaldi and so on even allow you to manually select the highlight instead of pre-picking based on the primary color.

Note: I am aware that given how trivial this is, it likely took a single frontend dev all of 10 minutes to create these. Still, these undermine branding efforts, and their names in particular do not suggest serious development work. There's a reason /u/Artorias38 correctly questioned whether these were even real. They feel like someone's first attempt at modding Firefox.