Solaris/Unix colour issues


I have a number of JGoAreas whose main component is a JGoRectangle.
I want these rectangles filled, so I use :
myRectangle.setBrush(JGoBrush.makeStockBrush(Color.lightGray ));
This works nicely on Windows, but is totally off the mark on Solaris and Linux - “gray” comes out as black, while “lightGray” and “white” both come out as white.
Does anyone have any idea why this is happening?