Thank you David.
I just picked yellow and white at random. I agree it wasn't the best choice :-p !
The method you provide for drawBitmap indeed draws in the whished colors, but it doesn't use the defined default background. By providing only one color, I would expect the method to use the defined background. drawText does, but not drawBitmap.
That's not an issue anyway, as there are many ways to workaround (including your suggestion). It was just a quick comment to make Jafleu and other readers notice that the use of the defined background is not straitforward in every drawing methods.