As can be seen here, this is the favicon of Winter Summer Bash site:
What is the meaning behind choosing those colors, in that order? (I don't remember when SE started using this icon.)
As I can see from my bookmarks, this favicon was already used last year, while the favicon in 2020 also followed this design theme already, but had slightly different colors:
so it seems to me just a way to point out graphically that it is holiday season and the Winter/Summer Bash is ON and no further specific meaning.
edit: the Winterbash 2022 favicon has changed in the meantime, following the same theme from the previous years, and looks like this: