It is called the gator bloodline and looking at pictures in the internet, they are bullies. Don't confuse them with Gator the pitbull, which is a real pitbull white in color and a red nose.
They are well proportioned and balanced. Pitbulls are muscular and colbys are no exception. Colbys tend to have a lot of white in their color with brindle patches. a few can be brindle and white...
I have seen them in black, dark brown with white nose, and tan. This dog turn to be dark colors. If you like shining black dogs look for chinaman, I hasn't seen this dogs except the chinaman...