I've had success changing sprite palettes by using the code logger function on FCEUX to narrow down the potential places in the rom where the arrangement of the sprites get referenced. One by one, I would alter the data in each of those sections until I found the one that altered the sprite I was looking for. (You're looking for big chunks of bytes that turn blue which means they are read) Be aware that it took a lot of playing around with the numbers for me to figure out the pattern of exactly how the tile addresses and palette selections were stored. Each game I've worked on handled the scheme a little bit differently. I'm most cases, there would be something like 3 bytes that handled the palette selection and the address in memory being referenced for each quadrant of the sprite. I was dealing with four tile sprites so the arrangement would something like A885D3 901920 A89890 14A520. The The first 3 bytes would handle the upper left tile, the 2nd set would handle the upper right, the third would handle the lower left, and the fourth the lower right. Within each of those sets, one of the nybbles (half of the byte) would alter the palette. You are dealing with a 6 tile sprite arrangement, so you would probably have 6 more additional bytes with each sprite arrangement.