Thanks for the info, Chris. But are you sure about only the PCjr having the capability to display the extended palette? We only had a bog standard IBM-compatible PC with an Intel 8088 CPU and CGA graphics adapter.
I remember reading somewhere (on this site perhaps?) that it was some kind of smart software thing that Sierra did.
Later, when we got VGA, and could now play the AGI games in EGA, the graphics was a big improvement even over the extended CGA. The EGA and CGA graphics looked very different, and not similar as you mention.