G'day all

I've taken it upon myself to try to create a 2d panel for the Carenado Saratoga. So far I've got a bmp image like such.

Attachment 64086

But here I've hit a bit of a wall. As I understand it the image needs to be indexed, and in the case of GIMP the maximum number of colours reduced to 255 so any pure black areas of the original panel image don't become transparent. But I'm at a bit of a loss on how to then make the window area pure black once I've done this. If anyone could give me a push in the right direction or point me towards a tutorial on panel design I would be very thankful.

Cheers

Az