Every Amiga 500 ever built had 64 color mode.
This is why games like Dungeon Master were so dam
depressungly disappointing with its puny 16 colors.
Dungeon Master was ported from Atari ST which only
allowed lame 16 color games.
The 64 color EHB mode was introduced in 1985 with
the A1000. Some A1000s came with the 64 color chip
while others did not. I know because I was there.
The most colors I ever personally programmed in any
AmigaOS game for the A500 was about 80. (Chaos WWII)
The most colors I ever personally programmed in any
AmigaOS game for the A1200 was about 6000. (Total Chaos)