Might help if you posted a couple of sample <a> elements to show which ones are red and which aren't.
I don't normally use FF for viewing source, so I'm not familiar with their color coding-- but this in turn means I haven't changed the defaults. Looks like all html entities are red. And in the sample page I looked at, the entire DTD was also red, with a popup saying rudely that they expected "doctype html" and that's all. Lissen, FF, it's entirely my own business what doctype I choose to use, so long as it's valid-- and in this particular case it was an e-book where we're not ALLOWED to use HTML 5 yet, so don't tell me, tell Project Gutenberg. Hmph.