It’s not just that the image is transparent though, because the color of the text changes too. I thought perhaps it’s using the site CSS to style SVG elements (which appears to be possible, though I haven’t tried it), but it turns out it’s just a CSS filter `invert(83%) hue-rotate(180deg)`. Still, it looks great and I’m impressed by the attention to detail.
Ah, serves me right for not seeing it myself and assuming it was just the background. Thanks for the additional info.