Or #f40 in CSS.
I see here there's no 420, so I'm gonna give 420420 a shot. :D https://news.ycombinator.com/topcolors
Make that #cbd420 - it doesn't add a light foreground for a dark background.
Edit: I figured it out. The user settings page shows the color - mine is set to ff6600 which was close enough to trigger parts of my brain.
Yeah it's just a bit off the standard one. I seem to remember getting it from an HN redesigned site or something.