Repainting in FSX

[gregg]

OK, I'm a novice at this. I have tried repainting an FSX aircraft by
repainting the .BMP file used in the aircraft textures. After I save my
modified file, FSX simply displays the parts of the plane I've repainted
(in fact, any parts included on that image "sheet" as black.

What am I doing wrong?

Help please

Gregg