This is very easy to do. You only need to set bit 5 on GTIA's PRIOR register. It's only a tiny change, but it is a code change.
Where the two sprites overlap you will get a third color.
I realized this was the cool ability I discovered while hacking Miner 2049erwhere they had the green helmet for Bounty Bob. I'd love to add this ability to the Moon Patrol sprite hack we are doing. I work mostly with hex editors so I was wondering what this PRIOR register would look like in hex?
I found this reference on De Re Atari:
Another question I have is: would the fifth bit also be the fifth mode? If so D6 and D7 would be 00?
But the main question so I can search for it in the code is what the hex code would be for the PRIOR statement?
Below is the graphics hack of Moon Patrol for the Atari 800 where the colors and sprites have already been altered. Combined color would offer a third color for the windshield on the moon buggy.
Here is the rom if you'd like to reference it for the above question on the PRIOR statement:
Edited by doctorclu, Mon Sep 24, 2018 7:14 AM.