You're staring at a palette. It's messy. You need blue, but the tube of Ultramarine is squeezed flat, looking like a stepped-on soda can. It sucks. Most people think you can’t make blue because it’s a primary colour. That’s what we were taught in primary school, right? Red, yellow, and blue are the "holy trinity" of the colour wheel. You can't mix them. Except, that’s not strictly true in the real world of messy, pigment-based physics.
Honestly, the "primary colour" rule is a bit of a lie. Or at least, it’s a massive oversimplification that ignores how light and chemistry actually behave. If you are trying to figure out how to make the colour blue with paint, you need to understand that you aren't just mixing "colours"—you are mixing chemicals that reflect specific wavelengths of light. Sometimes those chemicals play nice. Sometimes they turn into a muddy, greyish-purple disaster that looks like old dishwater.
The chemistry of why blue is so difficult
Blue is rare. In nature, it's actually one of the hardest pigments to find. Think about it. There are thousands of red flowers and yellow birds, but true blue? It's a freak of nature. Historically, artists had to grind up semi-precious stones like Lapis Lazuli just to get a decent smear of it on a canvas. This rarity is why the question of mixing it is so persistent. If you don't have a tube of Phthalo or Cobalt, you’re basically trying to trick physics.
In the subtractive colour model—the one we use for physical stuff like house paint or oils—the actual primaries are Cyan, Magenta, and Yellow (CMY). This is why your printer ink isn't red, blue, and yellow. If you have a true Cyan and a bit of Magenta, you can absolutely make a vibrant blue. But if you're working with a standard "student grade" set of reds and greens, you're going to have a much harder time.
Can you really mix blue from scratch?
Not really. Not if you mean starting with nothing but Red, Yellow, and White.
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If you take a warm red and mix it with a cool green, you might get a dark, moody shade that borders on navy, but it’ll never have that electric "pop." It will always feel a bit "off." This is because of the way pigments absorb light. To get blue, you need to subtract red and green light from the spectrum. Most red paints reflect a lot of orange and yellow light, which "contaminates" the mix.
However, if you have Cyan, you're in business. Cyan is essentially a very bright, greenish-blue. By adding a tiny, tiny amount of purple or magenta to cyan, you pull it away from the green side of the spectrum and push it toward a "true" blue.
Mixing the specific blues you actually want
Nobody just wants "blue." You want the blue of a stormy sea, or the blue of a clear June sky, or maybe that weird, glowing blue you see in neon signs. Every one of these requires a different strategy.
- Ultramarine vibes: If you have a blue that feels too "flat," try adding a speck of deep red or violet. Ultramarine has a naturally reddish undertone. It’s warm. It feels heavy and rich.
- Sky Blue (Cerulean style): You need white. Obviously. But don't just dump white into blue. Start with a pile of white and pull a tiny bit of blue into it. If it looks too "candy-like," add a microscopic dot of yellow. That tiny bit of yellow adds the "greenish" tint that high-altitude skies actually have.
- Navy and Midnight: This is where people mess up. They add black. Don't add black. Black paint often has a base of burnt umber or green, and it will make your blue look like mud. Instead, use a dark brown (like Burnt Sienna) or even a dark orange. Because orange is the complement of blue, it kills the brightness without killing the "blueness." You get a deep, vibrating dark that black just can't touch.
The trick with Phthalo Blue
Phthalo blue is the bully of the paint world. It’s incredibly strong. If you’re trying to use it to make a softer blue, be careful. One drop will overwhelm an entire gallon of white. But Phthalo is your best friend if you’re trying to mix a deep, transparent teal or a rich forest blue.
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If you find your blue is looking too artificial, the "expert" move is to add its opposite. Look at a colour wheel. Orange is across from blue. If your blue is screaming at you like a 1990s windbreaker, add a tiny bit of orange. It "greys" the colour down. It makes it look like something you’d actually see in the real world, like a shadow on a concrete wall.
Dealing with different types of paint
The "how" changes depending on what’s in your hand. Watercolors are translucent. They rely on the paper's whiteness. If you’re using watercolors and want a lighter blue, you don’t add white paint—you add more water. It’s about the "wash."
Acrylics are different. They dry darker than they look when they’re wet. This is the "wet-to-dry shift" that drives artists crazy. If you mix a perfect cornflower blue in acrylic, it’s probably going to look like denim by the time it’s dry. Mix it a shade lighter than you think you need.
Oils? Oils are the kings of blending. Because they stay wet for days, you can "mix on the canvas." You can lay down a layer of dark blue and scrub a little white or light green over the top to get a shimmering, "optical" blue that looks way better than anything you could mix on a palette.
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Common mistakes when trying to make blue
- Using "Primary Red": Most cheap reds have yellow in them. Yellow + Blue = Green. If you try to darken your blue with a yellow-based red, you’ll end up with a muddy olive.
- Over-mixing: If you stir the paint until it’s perfectly uniform, it can look flat. Sometimes leaving tiny streaks of the original colours—like a bit of violet and a bit of cyan—makes the "blue" look more alive to the human eye.
- Ignoring the "Temperature": Blues can be warm or cool. A cool blue leans toward green (like the ocean). A warm blue leans toward purple (like a grape). Decide which one you need before you start dumping other colours in.
The "Secret" Recipe for a DIY Blue
If you are truly desperate and have zero blue paint, look at your "cool" pigments.
Do you have a deep, cool purple (Dioxazine Purple) and a bright, cool green (Phthalo Green)? Mix them. Because the purple contains blue and the green contains blue, their "common denominator" is blue. The red in the purple and the yellow in the green will somewhat cancel each other out. The result will be a very dark, somewhat desaturated blue. It’s not perfect. It won't be "Royal Blue." But in a pinch, it’ll pass for a dark indigo.
Honestly, the best way to understand how to make the colour blue with paint is to stop thinking of blue as a single thing. It’s a range. It’s a vibration.
Actionable steps for your next project
- Buy a "split primary" set: Instead of just "blue," buy a "warm blue" (Ultramarine) and a "cool blue" (Cyan or Phthalo). This gives you the range to mix almost anything.
- The "Dot" Rule: When darkening or lightening blue, add the dark colour to the light colour in "dots." It’s much easier to make a light colour darker than it is to rescue a dark mess with half a tube of expensive white.
- Test on Scrap: Always. Acrylics lie to you about their final colour. Paint a small swatch on a scrap piece of paper, blow on it until it's dry, and then decide if it’s the blue you actually wanted.
- Use Complementary Neutrals: To make a blue "pop," don't make it brighter. Instead, put a dull orange or a warm grey next to it. The contrast will make even a muddy blue look like it's glowing.
You’ve basically got two choices: buy the right pigments (Cyan and Magenta) or learn to love the "near-blues" you can manufacture from purples and greens. Paint isn't math. It's more like cooking. A little bit of this, a dash of that, and eventually, you stop looking at the labels and start looking at the hue.
Go grab a palette knife. Start with a blob of white. Add a tiny bit of whatever "blue-ish" thing you have. Watch how it changes. That’s the only way to really learn.