This looks really really slick. The signup process only worked for me if I turned off tracking protection in Firefox.

One bug, entering hex code aggressively tries to convert 3 digit into 6 digit. So you can't actually type a 6-digit hex code because as soon as you type the first 3 digits, it expands it into 6, so you have to like backspace and mess around with it to get the color you want.

It would also be nice to have more flexibility in syntax highlighting section. Not everyone wants to group things in the same way for setting colors.