Color mapping is your choice. No one can say what your blue means.
For this particular exercise, I do not think there are text labels for output classes. As a ground truth, masks are provided. And, as you know, a mask include values from 0 to 22 corresponding to object types. But, again we do not know what 0 means, since there is no text label.
You can redefine by yourself, of course. It is a simple mapping between a value to text.
Looks like you posted the same question at here, and got a same answer already. Unfortunately, this exercise does not provide a text label…