The actual color of the button will indicate if a swap can be initiated, a swap can be made as a counter offer,
or if you have actually received a counter offer back for a swap that you initially created in the first instance.
a shift can be swapped.
this shift has been offered for a swap.
Another shift is made available to swap with.
shift has been offered up for a swap. And other shifts are available.
The swap has been agreed and is pending for approval from the planner/Traffic Manager
When the swap has been approved by the planner the button turns grey again, where it is possible to swap the shift again.