New colour to me. (Satin gold brown)

[Michelle.C]

Himalayan rats have no agouti genes in them, unless you bred an agouti to them they can't make agouti.

The rat in your picture is a Siamese, Himalayans are white typically with no body color except the darker points.
They are white because Himi's are not a pure genetic, they are half albino half Siamese, similar to a super stripe ball python is a yellowbelly and a specter combo.
Both genes land on the same locus, allelic to each other.

Mom is a black rat???

Check the picture he posted. The rat in the photos with the babies is 100% Agouti. It's just not that great of a photo.