fr55 simulator - black and dark grey not drawing

I'm just checking through the devices I want to support for my watch face and have noticed a problem in the simulator for the fr55.

When the colours are set to Graphics.BLACK and Graphics.COLOR_DK_GRAY nothing is drawn.

When the colours are set to Graphics.COLOR_LT_GRAY then white is drawn.

The code I have used to find this out is:

    targetDc.setColor(Graphics.COLOR_BLACK, Graphics.COLOR_BLACK);
    targetDc.clear();

And

    targetDc.setColor(Graphics.COLOR_BLACK, Graphics.COLOR_BLACK);
    targetDc.fillRectangle(0,  0, _screenWidth, _screenHeight);

The question is though. Is this a problem in the simulator or will it be on the watch too?

Unfortunately, I don't have access to a fr55 to test this on.

Many thanks,

Paul