Crossed black cow with a white bull. For some reason, all the calves received from them

Crossed black cow with a white bull. For some reason, all the calves received from them turned out to be black and white in maturity. Why did it happen?

The so-called recombination of genes has occurred – this is the birth of new combinations of genes, which leads to the appearance of new traits in the offspring.

Let’s consider this problem with an example:
Black color – A
White – a
The genotype in this case looked like this:
Cow – AA
Bull – aa
Accordingly, the offspring of the calves were with the Aa genotype