Here is a screenshot of the problem. As you can see, the game should always be using light blue but in this case it is trying to overwrite the pixels with the dark gray color.

I just tested it in ykhwong's latest build, same problem. It seems to be ok for a few lines then suddenly changes to dark gray. 😒

I recall that the overdraw problem on the statistics also occured on modern video cards playing the game in Windows. Perhaps it exploits a feature only found on older VGA and EGA cards. Otherwise I would suggest this is another bug in the program.

hmm I recall debugging this game once with harekiet.
it mixes int10 calls and raw register programming while updating the screen.
The game was broken as the no text showed up at all. Wrong mask or something like that.
Anyway to "cure" it you have to play a bit with the int10 calls that write to ioports.