I find the graphical feedback when pressing buttons (WKInterfaceButton) in watchOS2 is very weak. It is hard to see and even Apple seems to thinks this is the case as they e.g. in the unlock screen change the background to white on active buttons. The default behaviour is to dim the whole button.
How can I make a button press cleared in watchOS 2? I can e.g. change the button text color on activity but how do I easily change it back when it is no longer active?
There is currently no way to detect touch-down, or other events, on WKInterfaceButtons like you can on UIButtons on iOS. The only touch event you can detect is touch-up-inside, which calls the IBAction method.
Therefore what you wish to accomplish cannot be accomplished. Something you might consider is animating the button appearance once the action has been triggered. For example in my app upon button tap I animate the button's background color, then animate it back to the original color. That provides more visual confirmation to the user so they are certain the button was tapped.
I'd encourage you to file an enhancement request at bugreport.apple.com if you'd like to have more control with touch events.