[kevingadd]

The design of the windows approach to colored fonts actually has affordances for recoloring the text. It's not implemented, but it's mentioned in overviews of the format.

Because the colored glyphs use a palette instead of hard-coded colors, it's possible to assign semantic meanings or names to each palette entry and remap them. This would enable you to render a 'high contrast' version, or adjust the primary color of an emoji (for example, changing the skin tone of a face), etc.

The latter is actually a topic of concern: Most current emoji represent a caucasian or light-skinned individual, so the lack of emojis that represent other races is a problem. People are still figuring out how to deal with it.