For some reason my N function showed up in red even though I haven't noticed it in that color before. The color actually makes the code much more readable but I just don't know if I should be alarmed or not.

I applied a different stylesheet to my notebook (as you can tell by the color of the input I've been modding my own stylesheet) but the color is still there. I also checked on the Appearance tab of Edit > Preference and the only red syntax are the errors. I doubt "N" falls into any of these and I also can't tell which shade of red it is to match it to.

Update: this is getting weirder:
After restarting MMA, the N is no longer red :'( Also, I can't seem to File > Save Selection As without setting the window size to 100%. If the size is not 100%, I got the error that "The specified setting for the option WindowSize cannot be used."

This was reported to be a bug so I suspect my red "N" is also a bug (because previously, with the red N, I could save my selections at sizes that were not 100%). It was nice while it lasted I guess, though I really hope WRI adds better syntax highlighting in their future releases.
Nthat was on your path and Mathematica was warning you about potential name collisions or shadowing. Please see my answer in the linked duplicate for an explanation and a reproducible example. – rm -rf May 30 '14 at 14:33SetOptions[$FrontEndSession, "AutoStyleOptions" -> {"SymbolContextStyles" -> {"System`" -> Magenta}}](change to your favourite color) and use it for a while. If you like how it works, change$FrontEndSessionto$FrontEndand this will persist across sessions. – rm -rf May 30 '14 at 14:37