Or Black and Red? (Brown technically most of the time)
Seriously, it makes it hard to tell the difference for a lot of them too! There's Camponotus sayi, Solenopsis invicta, Dorymyrmex bicolor, Pogonomyrmex bicolor!?! On and on. What's up with this color scheme?
All these pictures are from http://www.alexanderwild.com/Antsif you couldn't tell