Exactly my first thought. This is one of the main reasons I frequent this site - I have tons of random tidbits like this cached in my head, so around half of the times someone introduces a problem to me, I am known to reply: "you know, X months back there was a post on Hacker News...".
I've had bugs in websites where menus would be completely messed up because they didn't fit in their given space, just because the font of choice was not available on Linux and it fell back on something slightly larger.
Edit: Though in the HN title it is much clearer than in the jsfiddle, for me anyway. Might that be it?
My font shows it as a missing character box.
I'm guessing that it just breaks the 'red' into a value which is interpreted as whatever the hex is. (See the chuck norris links posted in this thread).
Wow. I haven't seen a <font> tag in years
<blink>But pg made it!</blink>
• Ok, that is in fact green.
• I wonder if this is related to the colour name parsing weirdness that was on HN a couple of weeks ago?
• Heeeey, those aren't ASCII quotes!