I think basically what's happening here is that the font includes some SVG glyphs (for a bunch of emoji, no doubt). This causes us to render it via a "color font" codepath, and color fonts ignore the CSS
color property as the glyphs are painted with their inherent colors instead.
But in this case many (most) of the glyphs do not actually have color versions, and so they simply paint as black. We need to be making the decision whether to paint "as a color font" (ignoring CSS
color) on a per-glyph basis, not per-font-run, so that glyphs without inherent color don't just default to all-black all the time.