When it comes to lipstick stay away from orange. Orange tones tend to make teeth look more yellow and a lot of skin tones can't pull it off.
As for when to apply lipstick, believe it or not, it is RUDE to apply it in public or in front of co-workers. Yeah, I never really thought about it either, but apparently it looks cheap or unladylike. Hmmmm.
So if you are into having good manners, take your primping somewhere private!