The red looks great. I was originally going to go with the blue option (loved the look with the Surface 3), but after seeing the teal, I'm going with teal.
I have cyan, purple, and magenta for my SP2.
Black looks terribly boring but probably the worst part of the black keyboard is the gray felt on the back which looks terrible. Almost cheap.
I'm hoping these keyboard don't develop shiny spots (from oil wearing away the major keys). That was a big problem with my purple keyboard. The cyan was much more resistant (or perhaps the lighter color hid those spots better but it was probably use because I used the purple keyboard as my daily driver).