[fix] digit separator handling in Color parsing

[pq]

Add digit separator support to Color-parsing.

Fixes: #8510.

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[helin24]

@pq just curious, was this indeed a "good-first-issue"? I've often been guessing with that label. What made you pick up this issue?

[pq]

It would have been an easy first issue. I grabbed it because I was already looking at the color provider and was "in the neighborhood". That it was a quick fix was a bonus!

[helin24]

Cool! Maybe that could be an AI workflow, i.e. "are there easy issues I can fix while I'm here"