The number is a ceiling, not a target
In Pacyra the colour count is the most colours the engine may use, and it will happily use fewer. If a photograph genuinely resolves into 19 distinguishable colours, asking for 32 gives you 19. It does not invent 13 more to fill the quota.
That matters because in a printed kit the number is a promise about what is in the box, so 48 always means 48 pots. Here it means the engine has permission to go that far if the picture rewards it. Raising the number therefore never adds work for its own sake, which removes most of the risk from experimenting upwards.
The rule underneath it: two colours a painter could not tell apart on a palette never arrive as two separate numbers. So a larger palette buys you range rather than more mixing of near identical greys.
What each range actually buys
The useful way to think about this is not detail. It is how many decisions you are making at the palette before you are allowed to start painting.
- 8 and under. A poster. Large flat areas, strong graphic reading, almost no blending. Excellent for a group activity and for anybody who wants to finish something in an evening.
- 12 to 16. The range where a picture starts to look like the thing it came from while still being obviously a plan. This is the sweet spot for a first guide and most people who ask for advice should be pointed here.
- 24 to 32. Recognisably a painting. Enough range for a face to hold form and for a landscape to have air in it. Also the point at which mixing becomes a real part of the evening rather than a preliminary.
- 48 and above. Photographic. The guide starts describing the photograph rather than proposing a painting, and the number of colours you must mix and keep track of becomes the dominant task.
The cost nobody mentions
Every colour on your legend is a mix you have to make, match and keep wet. That is the part the kit sellers never have to discuss, because a kit arrives with the mixing already done.
At 12 colours you can lay the whole palette out before you begin and it will still be usable in two hours. At 48 you will be mixing while you paint, and every colour you remix has to match one you made earlier or the painting develops a seam where the two sessions meet.
So the honest guidance is the opposite of what the number suggests. If you are unsure, go lower. Finishing a 12 colour painting is a better evening than abandoning a 48 colour one, and the finished 12 will look more like a painting than the abandoned 48 ever would.
When a high count is right
Three cases, and they have something in common. In all of them somebody else has already done the mixing, or the mixing does not happen.
Digital work, where you are picking colours rather than making them. A printed canvas kit, where the paints arrive matched to the palette. And a reference you are looking at rather than painting from directly, where the count is buying you information about the photograph rather than instructions.
Outside those three, more colours mostly buys more work.
A practical way to choose
Set the physical size first, because it constrains everything after it. Then start at 16 and look at the result. If areas that should be separate have merged into one, raise it. If the page has filled with small shapes carrying colours you cannot tell apart, lower it.
Two or three passes settles it, and because the engine is deterministic you can return to a setting you liked and get exactly the same guide back.