I am very impressed how the 32-color Amiga version is close to the 256-color VGA version (and how much the Atari ST is lagging behind, more similar to the EGA version :)
The pirate close-up (pointed out by https://news.ycombinator.com/item?id=50495836) confirms: the Atari ST graphics are ported from the EGA version, while Amiga is based off VGA.
Was always jealous of friends with Amiga, the games always looked so much better than anything else at the time (helped by bigger tv's and scan lines no doubt).
The Amiga graphics chip had a palette of 4096 colors, you were just limited to 32 at the same time, or 64 with half bright tones, or more with chip/interrupt tricks. I doubt the latter was used on something like monkey island though.