I didn't mean paint traditionally and clean up, I meant, perhaps using a pencil sketch as base/ref, they painted it digitally in 24bit (possibly scaled), indexed. But I was stuck in a modern Photoshop mindset there. I don't know why, because I played the game back in the day.
I don't remember ever using the smudge/blur tool in DP, but now when you mention it, there might have been one. I'm not familiar with an 'auto antialiasing' tool though. I suppose these aa tools would throw hues into the gradients (closest match).
The game is older than I thought. In 1992-1993 when the game was probably produced, DP was still king (the 256 colors capable Amiga 4000 (aga) came in 1992). Yeah, I'm inclined to agree, these may have been made at 1:1 in index mode, although possibly based on a scanned sketch, because I suspect that game was at least storyboarded on paper.
I've seen some older games which have attempted a similar style, but it hasn't quite worked because of haphazard composition, low color count and excessive widepixel jaggies due to all the angles (making details hard to read).
http://www.abandonia.com/en/games/430/Black+Cauldron,+The.htmlI tried turning the DotT stuff into 16 color widepixels and it's actually not that bad for the less detailed screens.