Emoji heavy_check_mark: shown as pink instead of green

[suchAdemon]

Gitea Version

1.15.6

Operating System

Debian 10

Browser Version

Chrome 96.0.4664.45

Can you reproduce the bug on the Gitea demo site?

Yes

Description

I have seen that if I add :heavy_check_mark: to comments or something like that, it gets displayed in a different way based on the theme got selected, which leads to a miss understanding of it.

As you can see in the attached screenshots, it is green if the gitea theme is selected, but if you select the arc-green theme, it gets pink which leeds to a miss understanding of if

tested there as well: https://try.gitea.io/suchAdemon/test_sad

Screenshots

[silverwind]

Some emoji fonts like Apple's render this emoji in monochrome black, this is why we had it inverted using a CSS filter for better contrast. See https://emojipedia.org/check-mark/ for example renderings. I think it should be possible to change the invertion to preserve color, e.g. filter: invert(100%) hue-rotate(180deg) to fix this.