I'm new to GUI programming in C and Linux, and I'm having a hard time with it. It seems like a fairly simple/straightforward thing, but I can't find any answers googling. I want to add a background color to a widget. XmNbackground seems to be what I want to use, but I don't understand what I set it to, like a simple color blue, how do I get "blue" to set XmNbackground color to that?