I was wondering this too and poked around. Just 8 colors. And since a 16-dot pattern has 17 colors there were 17² ordered dithered colors, ie 4,913 possible ps

I was wondering this too and poked around. Just 8 colors. And since a 16-dot pattern has 17 colors there were 17² ordered dithered colors, ie 4,913 possible pseudo-colors. They had 8 primary colors (Black, Red, Green, Blue, Cyan Magenta Yellow White) in three bitplanes that would get OR-ed together. The coding scheme they used for their 8 primary colors is a bit redundant; if the hardware engineers had figured out a better pallet scheme using intermediate colors rather than Cyan/Magenta/Yellow/White, they could have had a lot more colors with pretty much the same hardware. For more explanation/details, see: https://www.hp9845.net/9845/hardware/9845c/ https://www.hp9845.net/9845/hardware/9845c/