Why are some calves born different colors?

Answer 1

Genetics. The genes in the momma cow combine with the genes from the calf's sire to create a calf with either the same colouration of the cow or not. What breed the calf's sire matters to. For instance, a Hereford sire bred to an Angus cow results in a black-baldy calf. Or, an Angus cow that has a recessive gene for Red colour and is bred to either a Red Angus bull or a Black Angus bull also with a heterozygous gene for the red gene can most likely produce a red calf. And the examples go on.

Answer 2

It's all to do with genetics. What colour the dam is and what colour the sire is may (or may not) determine what colour the calf will be. It's the genetics (or genotype) of both the sire and the dam that determine the colouration of the calf. For instance, a black bull bred to a black cow won't always give you a black calf. If both have the red gene in their genes, the cow may give birth to a red calf. A Hereford bull bred to an Angus cow will give a black-baldy calf. Jerseys bred to Herefords will give a brindle calf. It gets even more interesting if you breed a British White to a Hereford or a Longhorn to a Belted Galloway.