The albino is clearly a black animal that does not carry the RED gene. You need two copies of the RED gene to get beige animals.
The father does not carry any albino gene. You need two copies of the albino gene to get albino animals.
Albino is recessive
RED is recessive
The beige father was homozygous for the RED. The mother was an albino, but is genetically black. She did not carry the gene for RED.
That's why you got black rats.
If you breed any of those rats to the father, you will get beige rats.
If you breed any of those rats to the mother, you will get albino rats.