With regards to firing, the widget could potentially be modified to allow for different options depending on your need if that was desired. For my need, the slider has to fire as it moves to properly display the change in value in relation to some other values within my app, but the JS could be changed so that the event listener changed based on some input option. If you have some other solution you think would be better I’m open to that 
As for the singular style prop vs multi input props, I have tried to limit the number of inputs as increasing the number of input props for custom widgets currently leads to performance issues within the Tulip application. You can see more talk on that here: What we learned about custom widget, many props, and what not to do.
It’s a little more work, but you can still change the colors beyond initialization, you just would need to make a variable representation of the style prop object and modify that instead of a single color variable as you would otherwise.