Simply modify the colors in the bmp file for your model in the FMS 'model' directory. No need to go under metasequoia.
To drop a new color, you may use a 'fill' tool provided by an image software.
Save a copy of the original bmp file under another name before doing the modification.
Phil.
PS: for example, modify the yellow surface to another color in the bmp file that looks like:
and your plane turns from yellow to .....?