Espresso - AKA #2 - is a very dark cool-toned brown color. It's darker and has less gold in it then #4. In the wig comparison photo above left, a #1b wig is on the bottom with a #2 wig placed on top of it. You can see the #2 is definitely lighter brown compared to the natural black of #1b.

The two photos above show (left to right) 2, 4, 6 and 8 in the sunlight (first photo) and relative shade (2nd photo)