Zoo Tycoon

Every animal in the game that can be bred has a color variant.

To breed you must have an adult male and female in the exhibit with empty space (as soon as your female becomes pregnant the unborn animal will take up a space).

Make sure the animals are happy.

Build a breeding center and hire a lvl 3 (or train) breeder and assign it to the exhibit you want. Upgrading the breeding center only allows for more staff and doesn't increase your breeding chances.

At the front gate there is a research tree, you will need to research breeding to maximum (3 times) to increase your chances on a variant to 50% (along the way you will also increase your chances of breeding in general).

***never ran into this myself (i released all my animals at max level), but have been told that lvl 15 animals will not breed, just release any lvl 15 animals you get and replace them with the lowest level adults you can buy***