I can see it working well by combining colour settings with the "Comments" action.
Being able to use colour to soft group a bunch of actions together can work well to split up, sometimes pretty long action sequences residing in the same state. And having a comments action controlling the colour provides a header we can use to ...well comment the logic.
The way I'm seeing it working, is the Comments action can change the colour of all actions below it, until the next Comments action, next frame event action or wait action.
I think only the action title should have the colour change, not the background, so to avoid legibility issues.
I have concerns about having different colours based on the category the action belongs to, as i often use actions from a bunch of different categories to achieve a result, and it will just become a rainbow of colours, while still keeping the logic blocks hidden.
Edit 1: attached some mockup images
Actually after mocking it up, having the action backgrounds change colour as well, doesn't look too bad