Short answer: Choosing your undercoat (primer/base colour) is a strategic decision, not a coin toss. You match it to the model's dominant colour and the scheme you want: black for metallics and dark schemes, white or light grey for vivid colours like yellow and red, bone or light grey for Contrast and Speedpaint. The right undercoat works for you, cutting both coats and painting time.
In truth, "black, white or grey?" is less a single technique than a way of thinking. That is because your undercoat colour directly shapes your final scheme, the hours you spend, and how vivid your colours look. So instead of reflexively spraying everything black, split the model into zones in your head and ask: what is the dominant colour, and which colour is hardest to cover? The answer to those two questions names your undercoat.
What is undercoat colour and what does it do?
Let's start with the term. The undercoat is the first colour layer over your primer; very often the primer's own colour does this job, so it needs no separate step. This layer sets the ground beneath every colour you paint afterwards. A light ground makes colours glow, while a dark ground hands you depth and shadow for free.
So undercoat colour is a tool, not decoration. As Goonhammer's Zach puts it in a batch painting (painting many models at once) context, the right basecoat either makes every colour on top easier or saves you the most time. The trick is to decide by the model's needs rather than by reflex.
As Goonhammer's Zach sums it up: "Choosing the best basecoat for your models is an important step — I pick either the colour that makes everything on top easier, or the colour that saves me the most time." In other words, your undercoat is a tool that works for you.
How does it work? Value and saturation
Behind every undercoat choice sit two simple rules of physics. Once you understand both, the choice becomes almost automatic.
- Value sets the direction. A black undercoat pushes you to work "dark to light": shadow comes free, and you add the light. A white undercoat does the opposite, working "light to dark": brightness comes free, and you add the shadow. Pick whichever direction you find comfortable and your scheme demands.
- Saturation depends on the undercoat. Low-opacity colours like yellow, orange, red and light green pop over a white or light ground. The same colours go dull over black and force you into coat after coat.
- Time economy. Whatever the model's dominant colour is, priming in that colour (or a tone that eases it) cuts the number of layers, and so the time.
Light grey sits in the middle of all three: reasonable brightness plus a hint of shadow. That is exactly why, when in doubt, neutral grey is the safe middle path.
How do you decide, step by step?
It pays to settle the undercoat colour in your head before the brush touches anything. Work through this order.
- First, split the model into zones and find the dominant colour. Which colour covers most of the surface?
- Next, find the hardest colour to cover. Is there a low-opacity colour like yellow, red or white? If so, you may need a light ground.
- Then decide your scheme's "direction": shadow to light, or light to shadow? This chooses between black and white.
- Now factor in your paint system: Contrast and Speedpaint want a light ground, while classic layering (building colour coat by coat) is more forgiving.
- If the call is clear, spray it. Painting a single-colour army? Pick that colour's spray primer directly and skip the basecoat step entirely.
Which undercoat for which scenario? Ready recipes
Rather than solving the theory from scratch each time, you can lean on a few ready recipes. Pick the one closest to your model.
- Metal-heavy model (most weapons, knight armour, Space Marine pauldrons/shoulder plates): black undercoat. Metallics gain depth over black and the shadow arrives ready.
- Bright or vivid scheme (yellow armour, red cloak, white robe): white or light grey. Add a colour-specific midcoat if needed — a bone/cream base for yellow, for example.
- Contrast / Speedpaint workflow: light grey (Grey Seer type) or bone (Wraithbone type). Add a zenithal on top for the best result.
- Single-colour army (Ultramarines blue, Death Guard green): that colour's spray primer doubles as the basecoat, saving a step.
- Natural tones (leather, wood, bone, skin): a brown or bone undercoat saves real time beneath these tones.
Coloured undercoats have an artistic extension too. Advanced painters borrow imprimatura from classical painting — a thin, single-colour underlayer applied with artistic intent, like a pink-orange base for warm skin or a blue-grey base for cold metals. To go deeper, see Underpainting Methods.
Which paints and supplies?
On the priming side, sprays speed things up the most, but brushing on a primer works too. Keep these within reach.
- Spray primers: black, white, grey and coloured options (Citadel, Vallejo, Army Painter). The most practical route to a smooth, thin ground.
- Airbrush primer: ideal for control and zenithal transitions. A light grey base plus a white zenithal from above is the most-used combination.
- Coloured midcoat paints: tones that raise saturation, like bone/cream under yellow or pink under skin.
- Masking tape: handy for zone priming, when you want different undercoats on different areas of the same army.
Before you prime, though, make sure the surface is clean; even the best primer won't grip a greasy or dusty surface. We cover how in Cleaning, Mold Lines & Degreasing, and the priming itself in Priming & Undercoating.
The most common mistakes
Undercoat mistakes usually surface late, because the effect spreads across the whole paint job. These are the most common.
- Spraying everything black by reflex, then fighting coat over coat for hours on yellow or red.
- Priming white and never planning the shadow; the result can look "washed out" and pale.
- Using Contrast paints over a black undercoat — you lose most of their effect.
- Choosing the undercoat colour by habit, divorced from the scheme.
- Spraying too close or too thick and drowning the detail; thin coats are always safer.
Pro tips
A handful of habits also make the decision reflex faster. They save time and nerves at the table.
- Always split the model into zones when deciding, and ask: "what is the dominant colour, what is hardest to cover?" The answer names your undercoat.
- Use zone priming on the same army: prime the body black, then prime later-added white shoulders separately by masking or carefully leaving that area white.
- When in doubt, pick neutral grey; it is the safest middle path, offering both reasonable brightness and a hint of shadow.
- Spray white from above onto a light grey base for Zenithal Priming; that way you get a light-and-shadow map for free.
- Thin your first colour as you leave the primer behind; the Thinning Paint: Two Thin Coats logic is the key to covering without burying your undercoat ground.
Frequently Asked Questions
Should I prime black or white?
It depends entirely on your scheme. Black is faster for metallic, dark, shadow-heavy schemes because shadow comes ready. For vivid, low-opacity colours like yellow, red and white, on the other hand, pick white or light grey; these colours pop over a light ground with far fewer coats.
When is grey undercoat best?
Especially when you're undecided and want flexibility. Neutral grey gives both reasonable brightness and a hint of shadow, so it's neither too dark nor too light. It's also the ideal ground for Contrast and Speedpaint systems, where colours sit down naturally and balanced.
Which undercoat do Contrast paints need?
Light grey (Grey Seer type) or bone (Wraithbone type). Contrast paints are translucent and rely on the ground beneath them, so over a black undercoat they lose most of their effect. For the best result, add a light zenithal over the pale undercoat.
Why is painting yellow or red so hard?
Because these colours have low opacity and can't hide the dark ground beneath them. They go dull over black and demand coat after coat. The fix is simple: a white or light grey undercoat, or a colour-specific midcoat — a bone/cream base layer under yellow, for example.
Can I skip a step when painting a single-colour army?
Yes. If you find a spray primer in the same colour as the model's dominant tone (Ultramarines blue, say), that primer doubles as your basecoat. You skip the separate base-colour step entirely and save serious time in batch painting.
What is a coloured undercoat, and is it the same as imprimatura?
A coloured undercoat is an underlayer that eases the dominant colour. Imprimatura is a thin, artistically intended underlayer borrowed from classical painting: pink-orange for warm skin, blue-grey for cold metal. Really, both are levels of the same idea — making the ground work for the colour.
Can I paint as soon as the primer dries?
Spray primer is touch-dry in minutes, but it's wise to wait at least 20–30 minutes for it to cure, ideally a few hours. That's because if you paint too early the primer can stay tacky and hold brush marks. Don't rush; a fully set undercoat anchors every layer that follows.
Key takeaway and next step
In one line: undercoat colour is a strategy, not a default. Split the model into zones, name the dominant colour and the hardest to cover, choose your scheme's direction — the rest follows. In short, black for metallics, white or light grey for vivid, bone for Contrast, neutral grey when undecided.
Once you've picked the right undercoat, every layer after it flows far more easily. If you want to kit out your bench or fill the gaps, browse our paints, brushes & hobby supplies; every model that starts on the right ground finishes faster and cleaner.