Your co-workers sound incredibly rude? Or is that just the jargon where you work?
Anyways....
-Make sure you wear a mascara that doesn't dry up & crumble, because then it'll settle below your eyes and make it look like you have dark circles
-Avoid pink or reddish eyeshadows when you're tired
-Use a light-reflecting under-eye concealer (such as dior skinflash, loreal touche magique, etc., every brand offers one of those now). Make sure to use an eyecream first so the concealer will be easy to apply
-Wear some kind of blush or light bronzer to add some colour to your face
-Ditch the eyeliner if that's what makes you look tired
Hope that helps.