There are 6 variant colors for this, each one for female and male medium Mii heights. You can choose between red, green, pink, orange, yellow and purple (doesn't this remember you to some famous plumber guys and princesses?) I'm going to add more colors in future actualization.
There are some little details I would like to talk about: Since Mii heads are not always the same size due the head shape, hairstyle and face props, there's not an exactly plumber cap size, so I gave them a unique cap size and this may not look correctly on Miis that has hats on their heads.
The download contains the kart files over all vehicles, driver menu model, award model and allkart file for the selection screen. There was so many textures I had to make, since there are 72 vehicle textures for 6 color variants, so I want to apologize if some of the kart textures are mixed up with other colors that doesn't match. Of course I'm gonna fix this in a future actualization as I said.
As a last thing I would like to state, I didn't experience any bugs while I was playing, but since this is my first mod that includes custom 3D models I don't doubt there could be few bugs, please notice me if you experience something while you play.
Special thanks to MattyGaming because he helped me adding the second shadow layer to the model to look good in-game.