The whole point of an ActiveX control is that is a black box whose inner workings you do not need to worry about. And that can be great, and save you a lot of time and effort The downside is that an ActiveX control only exposes methods and properties the designer thought useful and/or appropriate. And if they decided not to expose the background colour as a property then you are out of (direct) luck.
Thing is the Active controls are often made up of standard Windows controls, which provides us with a backdoor or hack for achieving what you want. Several problems, though. Firstly you need to be able to identify the Windows control (or controls) whose background property you want to change, and you need to identify the Windows class of those controls. Then you need to read the MSDN documentation on which message you need to send that particular class of control to change its background colour, then - from the sounds of it - you are going to have to read the MSDN documentation about how to send a message to particular window. The example you linked to above is an example of an implementation of one such a hack.
You'll appreciate that, in the situation where the control's author has specifically excluded the background colour property they are unlikely to provide you with documentation about how to hack the control.
