I believe I have found a bug with XControl properties. It is illustrated in the attached image.
Selecting the Style property results ina Style ID property node on the block diagram. I also renamed the property to Color Style, and got the same behavior. I have not noticed any issues with the other custom properties.
There are a set of specific names for property nodes which should NOT be used for custom properties in XControls (like "Label"). I also ran into the exact same problem before where I named a Property and then when trying to access it, got a completely different property (and datatype) back. It seems there can be some serious name collision issues with XControl properties which are not documented anywhere.
I requested this to be either changed or at least documented before.