In the update script, MINIMIG or FXCAST, if there is no color in some areas these areas are green.
I tested 3 VGA screens of different brands and with 2 different video cables, the result is the same, so I have some games with green instead of black.
This makes me think that programmers of the 8/16 bit era used the absence of color to have black in order to gain a few bytes on the floppy / tape.
Maybe the MISTer.ini file is the solution ?
Thanks for your help.