Acrylic, watercolour, gouache, coloured pencil or marker — what each does to printed paper, and how to match your medium to the sheet you generated.
By Yvgeny Konrad · 5 min read
A printed color-by-number sheet is paper with ink lines on it, and different media treat that very differently. Some will buckle it, some will dissolve the lines, and some will cover the numbers so completely that you lose your place.
Here is what each option actually does, and how to choose.
Region size. A sheet with hundreds of small regions rules out anything with a fat tip. If your smallest regions are a few millimetres across, a brush pen or a chunky marker cannot reach into them.
Opacity. Every medium eventually covers the printed number. Opaque media hide it on the first pass, which means you should work in batches — paint every region of colour 1, then every region of colour 2 — rather than working area by area and losing track.
If you have not printed yet, both constraints are still adjustable. Raising Cell size and Min region in the generator produces larger regions, which opens up more media.
Best for: detailed sheets, children, anyone who wants to be able to undo.
Coloured pencils are the most forgiving option and the best default. They work at any region size, they do not touch the paper's shape, and they build up gradually so you can stop when a colour looks right.
They are also semi-transparent, which is genuinely useful here: the printed number stays faintly visible through light shading, so you can check yourself as you go.
The trade-off is coverage. Getting a solid, even fill over a large area takes real effort, and cheap pencils will leave visible stroke texture. If your sheet has large flat regions, this is the medium's weak point.
Practical note: sharpen more often than feels necessary. A blunt pencil cannot get into a corner, and corners are where the borders are.
Best for: landscapes, soft subjects, adult projects on proper paper.
Watercolour is beautiful on a color-by-number sheet and the most demanding to print for. Standard copier paper will buckle the moment it gets wet, and once buckled it stays buckled.
If you want to use watercolour, print on paper of at least 190 gsm — watercolour paper if your printer will take it. Many home printers handle up to around 200 gsm through a rear feed but not through a bottom tray, so check before you buy a ream.
The other consideration is your printer's ink. Dye-based inks — common in cheaper inkjets — will run when wet, and the borders will bleed into your washes. Pigment-based inks and laser toner stay put. Test one sheet before committing to a large project.
Watercolour stays transparent, so the numbers remain visible throughout. That makes it forgiving in the one way that matters most.
Best for: bold results, large regions, the closest thing to a commercial paint-by-number kit.
Acrylic is what commercial kits ship with, and it gives the most striking finish: fully opaque, richly coloured, and permanent when dry.
It is also the least forgiving. It covers the number on the first stroke, it dries within minutes and cannot be reworked, and it needs heavy paper — 200 gsm or more — or the sheet will warp badly.
Thin it slightly with water. Straight from the tube, acrylic is thick enough to hide the printed borders as well as the numbers, and once you have lost a border you are guessing.
Work colour by colour, not region by region. Mix one colour, find every region carrying that label, paint them all, then move on. This is the only reliable way to work with an opaque medium.
Best for: anyone who wants acrylic's coverage without acrylic's finality.
Gouache is opaque like acrylic but re-wettable like watercolour, so a mistake can be lifted with a damp brush instead of painted over. It dries to a flat matte finish that suits the graphic look of a color-by-number sheet particularly well.
It needs the same heavy paper as acrylic, and it is generally more expensive. But for adults working on a detailed sheet, it is arguably the best match for the format — opaque enough to look finished, forgiving enough to enjoy.
Best for: children, speed, sheets with large regions.
Markers are fast and satisfying and produce vivid flat colour with no effort. For a classroom or a rainy afternoon they are hard to beat.
Two warnings. Alcohol markers bleed through standard paper — put a spare sheet underneath or print on something heavier. And most marker tips are too broad for small regions, so if you are printing for markers, generate the sheet with a larger cell size rather than discovering the problem after printing.
Water-based felt tips bleed less and are the safer classroom choice.
| If you want… | Use | |---|---| | Fine detail and the ability to correct | Coloured pencil | | Soft, atmospheric results | Watercolour on 190 gsm+ | | The commercial kit look | Acrylic on 200 gsm+ | | Opacity but still forgiving | Gouache | | Speed, or a room full of children | Water-based markers |
The useful realisation is that this decision runs in both directions. If you already know what you will be painting with, generate the sheet to suit it:
One more thing worth doing regardless of medium: print a test page first. A single sheet tells you whether the numbers are readable at your chosen size, whether the borders survived your printer, and whether the paper can take what you are about to do to it. It is a much cheaper lesson than discovering the problem twenty regions into a project.
Generate your sheet at ColorByNumber.art, download the SVG for the sharpest lines, and test one before you print the set.