How to access the UI elements from nodes?

Has anyone played with the new elements of the UI other than text, I am trying to figure out how to make a slider or button truly work to start with.

For the button I can set it up and make it function but have no access to the color of the button or seem to be able to add a image to it. Has anyone figured this out?

For the slider, again I can add it to the UI builder but how do you access the color and position of the slider?

I am using nodes in my projects, I am more then willing to drop in some code if anyone has an example and can explain how to access the variables in the code from the node treee I am building.

Hope that explains everything well enough.

I haven’t looked at it myself, however usually for things like that in other engines I’ve used you can subclass the button and then change it’s properties that way.