Whats with the white stripe ?
Thats something to do with how the game renders and shades the tread's texture diffuse map. It will always turn any color you paint it into grey. Even if you paint the texture as pink, it will be rendered grey. So, at the moment, this is the whitest it can get.
I and vlasovas tried so many things to try and change this, but have not found any that works properly to still make the tread wear, effects and wet treads work.