you can get the stdColor from com.ptc.pfc.pfcBase.stdColor.COLOR_HIGHLIGHT. I don't check if u can cast StdColor to RGB Color or not. If u can't I think theres no way directly in J-Link to get it except a Mapkey / Trailfile.
I know that in Toolkit you can get both direct to ProTextStyleColorSet() or the other color set functions. So it's possible that the J-Link command do it the same way.
typedef struct pro_color
Other way around you can use a .dll File from your J-Link application to get the Toolkit command inside your J-Link program.