System colors are being implemented in Servo, and it seems to me it would be easier to treat the deprecated ones as aliases:
<!DOCTYPE html>
<script>
var { style } = document.documentElement;
style.color = "ActiveBorder";
document.write(style.color); // "activeborder". Why not "buttonborder"?
</script>
https://drafts.csswg.org/css-color-4/#deprecated-system-colors
https://drafts.csswg.org/css-color-4/#resolving-other-colors
System colors are being implemented in Servo, and it seems to me it would be easier to treat the deprecated ones as aliases: