One interesting piece of information is that the green tomato one finds in Mexican sauces is actually a different variety from the red tomato.

The green tomato stays green and comes with a papery wrapping around it: in Mexico is called simply tomate, in the US it is known as tomatillo. In Europe it is not called at all, since it is unknown.
The tomato-that-eventually-turns-red is called jitomate, and it also used in making salsa (both cooked and raw).