@lempkee:
HAM is 4096 colors from a pallette
256col means 256.000 colors
HAM has a 12bit scope, meaning, it has (2^4)*(2^4)*(2^4) combination of colours [4096 (2^12)], and 16(2^4) levels of gray.
AGA had 256 registered colours out of a 24bit scope, and 256(2^8) levels of gray.
But if you had a palette of 16bit as in some VGA cards, you would only have 256 colours out of a palette of 264.112, and 64(2^6) levels of gray.
The 264112 colours of AGA are due to HAM-8 mode were it only had 2^6 levels of gray from a 16Bit scope
@lando:
You can't really use HAM with dynamically animated objects - the backgrounds may be static but the characters and so on are all animated. The colour of each pixel depends on the colour of the previous pixel, so you'd get streaking all over the place as the characters moved around in front of the background.
Although HAM isn't used because of speed and the fringing effect, there were other ways to bring more colours on A500. Universe was an example with 256 colour at the same time.
But Lucasarts weren't really making much use of the Amiga chipset, it was like you say just a cheap PC port (shovelware).
Lucas Arts made use of the copper, it used multiple screens, one for the gamescreen and another for the functions menu and inventarium which should had give it at least 64 diferent colours at the same time.
