If you have been making Bath Bombs for any length of time, then you’ve probably tried to make Purple by mixing Red 40 and Blue 1, and–congratulations–you made GRAY! It’s almost a right of passage. It seems every bath bomb maker has to go through this! But have you ever wondered why this happens? Afterall, we were taught in Kindergarten that Red and Blue mix to make Purple. When you look at a color wheel you can easily see this should be the case. Instead, as makers, we have to learn (usually the hard way) that Red 27 and Blue1 make Purple. Red 27 is the color most people would call Pink! 

Why?! Why does this happen?

I hate to break it to you, but your whole life is a lie. Or at least, all the color theory you’ve been taught is a lie! 

When I taught art there was a lesson I loved to teach called, “Pink is not a Color.” It was great because the students were always outraged. They would adamantly defend Pink and claim that it had to be a color. So let’s talk about Pink real quick, and then I’ll get back to Purple.   

If you look on a traditional color wheel you will not see the color Pink. Instead Red and Yellow transition through 3 steps of Orange-ness to get to each other. Yellow and Blue transition to each other through tonalites of Green. Blue and Red transition through Violets until you get to Purple, at which point you find yourself abruptly back at Red.


So where’s the Pink? Arguably, Pink could be considered a tint of Red. Tints are created by the addition of white pigment, and while you can get nice soft Pink tones, this still only proves that Pink is a tint of Red, not a true color in its own right. 

“But wait a second,” I hear you say, “I just googled color wheels and I saw plenty of them that had pink!.” Ahhh, I like that fighting spirit my friend, but sadly, you’re still wrong! The Pinks you saw were actually Magenta, and that Color Wheel was using CMYK. The reason for that is SCIENCE! 

Issac Newton was the first person we know of to look at the rainbow of colors coming out of a prism and to assimilate the idea that white light is made of many different colors. He believed that color existed within a closed wheel. But–hello Issac!–when light breaks from a prism and creates a rainbow it does so in a linear fashion. Light, we now understand, is a spectrum, not a circle, and the amount of light visible to our eyes is very limited. 

Newton was correct though, the combination of Red, Blue and Green create WHITE LIGHT within a system of color called RGB, or Additive Coloring.

RGB Color Mixing: Source

Bath Bombs however, are not made of light, and are therefore subject to a system of coloring called Subtractive Coloring. 

Subtractive Coloring works within the bounds of CMYK–a process used for printing with dyes and pigments. Those sound familiar right? For this color system, you start with white, and the colorants SUBTRACT, some of the whiteness that is being reflected and sent to your eye. Basically, any solid object you see is using some form of Subtractive Coloring.

CMYK Color Mixing : Source

In CMYK, or subtractive color wheels, we finally see not just Pink (or Magenta), but also Purple. And, while we did find Purple in the original color wheel, that was in a system oriented to light. So unless your bath bombs are made of actual light (in which case you are amazing!) you’ll need to learn to mix them with CMYK on your mind and not RGB. 

If you begin to think of the Lakes or Dyes you use as aspects of CMYK, then this whole thing will quickly make sense.

  • C-Cyan= Blue 1
  • M-Magenta= Red 27
  • Y-Yellow= Yellow 5
  • K-Black= Achieved by mixing all three, enhanced by adding Red 40, and Yellow 6

A good rule of thumb is that the colors Blue 1, Red 27, AND Yellow 5 will all work together beautifully. And the colors Red 40 and Yellow 6 will also work together beautifully (although with obvious limitations). However, by mixing these two color families together, you will get darker, more muted colors. So unless you want gray, you should probably steer clear of combining these two color families. 

In art we talk about color in terms of its

  • HUE: the obvious  color (green, red, blue etc)
  • VALUE: the lightness or darkness of a color
  • CHROMA: Saturation or brilliance of a color

For this experiment I create HUES of Purple using Lakes. Red 27 and Blue 1 are the focus, but I also throw in a nice Gray just in case you’ve never had the joy of doing that yourself! I used 250 grams of Bath Bomb mix (minus the citric acid) for each color tested. 

Red 40, Blue 1 & Red 27

I used ratios to make it easier to scale the colors up or down in the future, and wrote them on the lids of each mix. The mixes are supersaturated, but you can begin to get an idea of how to achieve the colors you want. 

Whether your batch is large or small, you can use the ratio as a guide and continue to add colors to your bath bomb mix until the saturation is correct for your batch size. Make sure you write down how much you need for your batch!

Write it down!

If you use Lakes, make sure you use Polysorbate 80! I have never had issues with my tub staining, even in super saturated mixes, as long as I use Poly 80!


A ratio is a simple expression of how much of one thing there is to another! They are read part to part, meaning that a ratio of 2 apples to 3 oranges could be expressed as 2:3. If you want to express the same number of oranges (3) to the same number of apples (2), you would say 3:2. It’s a very easy way to enlarge or reduce ingredients.

For my Bath Bomb color mixes I used the following ratios and amounts:

Purple Bath Bomb Color Mix 1

  • Red 27:Blue 1 — Ratio 4:1 
  • Actual Amount — 1 tsp: 1/4 tsp
Purple Bath Bomb Color Mix 1

Purple Bath Bomb Color Mix 2

  • Red 40:Blue1 — Ratio 2:1
  • Actual Amount — ¼tsp: ⅛tsp
Purple Bath Bomb Color Mix 2

Purple Bath Bomb Color Mix 3

  • Red 27:Blue1 — Ratio 2:1
  • Actual Amount — ¼tsp: ⅛tsp
Purple Bath Bomb Color Mix 3

Purple Bath Bomb Color Mix 4

  • Red 27:Blue1 — Ratio 1:1
  • Actual Amount — ½tsp: ½tsp
Purple Bath Bomb Color Mix 4

Purple Bath Bomb Color Mix 5

  • Red 27:Blue1 — Ratio 8:1
  • Actual Amount — 1tsp: ⅛tsp
Purple Bath Bomb Color Mix 5

If you notice, the Mix 1 and Mix 5 samples are technically the same color. The Chroma, or saturation, is different, but the Hue is the same. You can use similar techniques when coloring bath bombs to create a wide range of colors in every shade imaginable. The possibilities are endless when you begin to mix your own colors! 

Here they all together for comparison.

About Robyn French Smith

My name is Robyn French Smith! I studied fine art at the University of St Thomas and the Glassell School of Art in Houston TX, and graphic design at The Art Institute of Houston. I started dabbling in DIY bath and body products over 10 years ago after moving to Alaska. While I knew how to make basic soap for several years, I didn’t start looking at it as an art form until about 4 years ago when a neck and shoulder injury made it almost impossible for me to draw and paint. I needed a place for all that creativity to go, and I found it in soap. I received my Basic Soapmaker Certification from the HSCG in 2019 and plan on pursuing further levels of certification.

Find me online at scandaloussoap.com and Facebook!