Mix roughly equal parts red and blue food coloring to get a basic purple shade. The key to getting the purple you actually want, whether that’s a soft lavender or a deep royal violet, is adjusting the ratio and adding blue slowly. Blue is a much stronger pigment than red, so a little goes a long way.
The Basic Ratio
Start with more red than blue. A good starting point is about 3 drops of red to 1 drop of blue, then adjust from there. McCormick’s official mixing guidance recommends beginning with a red base and adding blue gradually in small increments until you reach the shade you want. If you dump equal amounts of both colors in at once, you’ll almost certainly end up with something too blue and difficult to pull back toward purple.
Mix your colors into a small amount of whatever you’re coloring (icing, batter, water) before committing to the whole batch. This lets you test and tweak without wasting ingredients.
How to Get Different Shades
The ratio of red to blue determines where you land on the spectrum between pink-purple and blue-purple. Here’s how to aim for specific shades:
- Lavender or lilac: Use very little dye overall. One drop of red and one tiny drop of blue in a large amount of white icing or batter gives a soft pastel. The lighter you want it, the less total dye you add.
- True purple or violet: Use roughly 2 to 3 parts red to 1 part blue. This balanced mix gives the classic purple most people picture.
- Deep royal purple: Increase both colors significantly, keeping the same ratio but layering more dye. You can also shift slightly toward more blue (closer to a 2:1 red-to-blue ratio) for a richer, darker result.
- Plum or wine purple: Lean heavier on the red, using 4 or 5 parts red to 1 part blue. This creates a warm, reddish purple.
With any shade, build color gradually. You can always add more dye, but you can’t take it out.
Why Your Purple Might Turn Muddy
If your purple looks grey, brown, or just dull, the most common culprit is trace amounts of yellow in your red dye. Red food coloring that leans orange (meaning it contains some yellow pigment) will produce murky results when mixed with blue. Yellow and blue make green, and that green undertone fights the purple, dragging it toward brown or grey.
To avoid this, use a red that looks true red or slightly pink, not one that tilts toward orange. If your food coloring set has a separate “pink” or “rose” option, try using that instead of the red. You’ll get a cleaner, more vibrant purple.
Another common cause of dull purple is the base you’re mixing into. Yellow-tinted ingredients like butter in buttercream frosting act the same way a yellow dye would. The yellow in the butter mutes the purple. White icing made with shortening or cream cheese produces much brighter results than butter-heavy frostings.
Fixing Grey or Dull Purple Frosting
If you’ve already mixed your frosting and ended up with a disappointing grey or washed-out purple, there’s a fix that actually works. Heat helps food coloring pigments develop more fully, a process bakers call “blooming” the color. Scoop out a small portion of your frosting, microwave it for 5 to 10 seconds (just enough to slightly soften it, not melt it completely), then mix it back into the rest of the batch with a hand mixer or stand mixer.
If the color still isn’t deep enough after remixing, repeat with another small portion. Only microwave a little at a time so you don’t break down the whole batch. An immersion blender can also work because the heat generated by the blades helps the color bloom in a similar way. Let the frosting rest for 30 minutes after mixing, too. Food coloring often deepens as it sits.
Gel vs. Liquid Food Coloring
The type of food coloring you use changes how much you need, but not the ratios. Gel food coloring is far more concentrated than liquid drops. A single toothpick dip of gel paste can equal 5 or more drops of liquid dye. If you’re using gel, start with the tiniest amount you can manage and build up.
Liquid food coloring requires a lot more product to reach deep, saturated colors. That’s fine for most purposes, but in recipes where extra liquid matters (like macarons, royal icing, or candy), the added moisture from many drops of liquid dye can throw off your consistency. Gel paste avoids this problem because you need so little of it. For everyday projects like coloring frosting for cupcakes or tinting water for a craft, standard liquid drops work perfectly well.
Making Purple With Natural Ingredients
If you want to skip synthetic dyes entirely, red cabbage is the simplest natural source of purple. Cut a red cabbage into pieces, boil them in water, and strain out the solids. The resulting liquid is a natural purple that works in frostings, batters, and drinks. One interesting property: adding a small amount of baking powder shifts the color from purple toward blue, so you can fine-tune the shade with a tiny pinch.
The tradeoff with natural dyes is intensity. You’ll need more liquid to get a noticeable color, which can dilute whatever you’re mixing into. Reducing the cabbage water on the stove (simmering it until the volume shrinks by half or more) concentrates the pigment and helps solve this problem. The flavor is mild enough that it disappears in most sweet recipes.