Congrats on proving her to be a het dumbo, and yes blue is a recessive trait also so mom is also a het blue.

That blue dumbo baby is a cutie and Dobies, I love Dobies, lucky you!

The white on the Blues belly I believe is called Irish, or English Irish, lol, I'm not positive which but it's not a self and not a Berkshire.

That black one is a variegated Berkshire or Variberk as they are called.
It's actually one of my favorite patterns in a rat, that and the possum face blazes like that blue variegated girl rat you have there, super cute.