So I was looking to upgrade one of my skills and noticed that Packmaster was colored blue. At first I thought that the blue colored upgrades were the selected upgrades when more than one are unlocked (e.g. Domination), but in the case of Packmaster, that's the only available upgrade for that skill. None of the others are colored this way, they're just white or greyed out. And it can't be a story unlock, Packmaster was just a regular upgrade.

What does the blue color for the icons indicate?

[![blue Packmaster](https://i.stack.imgur.com/qj5KF.jpg)](https://i.stack.imgur.com/qj5KF.jpg)
*Domination is blue, but Packmaster is as well*