Currently, when using the enhanced board view/UI update for kanban boards, the epic label is no longer applied to epics. You can still change the color in the Epic itself and it'll be updated there and the backlog, however the board view has removed this feature. For some users, this feature was useful in quick sorting/getting a better view of all epics in a quick glance. Rather than removing this feature, making it a toggle would be better in the end to allow users themselves to decide whether this is something they want or don't require.