I made these intense Rainbow bath bombs, and was really excited to see how vivid the colors looked together.

Before the bath bombs were dry, I had someone ask what color the final bath water would be, commenting that rainbow bath bombs generally turn the water a disgusting brown color.

I hadn’t tub tested the bath bombs yet, but I knew by looking at the colors I’d used, that the end water would be a hunter green color. Sure enough, I was right!

But how did I know this? And how would you be able to tell what color your end water will be?

Questions about use of color in Bath Bombs are one of the most common things I see posted on Facebook forums. Generally it will be phrased something like this, “If I mix this color with that color, will my bath water turn out brown?

This article will cover the use of Lakes to make Greens. I’ll be doing a color study for each color family over the next few weeks. While these colorants are Lakes, not Dyes, many of the principles will remain the same. If you’re supplied with the basic colors Red 40, Blue 1, Yellow 5, Yellow 6, and Red 27, you can create any color on the planet.

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 work together beautifully (although with obvious limitations, since orange is about all you’ll achieve). However, by mixing these two color families together, you will get darker, more muted colors.

Coloring with pigments and dyes uses the process of subtractive coloring. Subtractive coloring usually works within the bounds of CMYK–a process used for printing. For this color system, you start with white (plain bath bomb mix), and the colorants SUBTRACT, some of the whiteness that is being reflected and sent to your eye. C-cyan (Blue 1), M-magenta (Red 27). Y-yellow (Yellow 5).

Then there is Red 40 and Yellow 6. Where do they come into play? You can think of these two as being the K(Black) in CMYK. Red 40 and Yellow 6 work great on their own, but when added to the other colors, they begin to desaturate and darken the color value. You’ll be able to quickly get a grasp on how to mix colors when you learn to think of them this way.

Why would you want to blend when you can purchase beautiful pre-mixed Lakes and Dyes? If you use pre-mixed colors then you don’t know how much of each base color was added to achieve that gorgeous teal. As beautiful as it is, do you know if it has Red 40 in it to make it a bit darker? Did the person who mixed it use Yellow 6 or Yellow 5? And if you want to pair that beautiful teal with pink, will it be better to mix it with a dash of Red 40 or a pinch of Red 27? If you learn to create your own blends, you’ll never have to be worried about brown bath water again.

Don’t get me wrong, having lovely pre-blended colors ready to grab and use is super convenient, but if you want full control over the end water, you really need to learn to mix them yourself!

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

To make Green we need Yellow and Blue. We will control the HUE by adding more or less of the Yellow and Blue. We will control the VALUE when we add Yellow 6 instead of Yellow 5–adding Yellow 6 will darken the color. The CHROMA is controlled when you scale the ratio up or down for your batch–more mix with less color creates diluted colors. Perfect for pastels!

Yellow 5, Blue 1 and Yellow 6 (Lakes)

For this experiment I used 250 grams of Bath Bomb mix (minus the citric acid) for each color tested. Then I used ratios 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, if you wanted the appley-acid-green in Mix 5 (below), you would continue to add Yellow 5 and Blue 1 according to the ratio, until the saturation was correct for your batch. Make sure you write down how much you need for your batch! From now on you’ll always have the right color! You could even go further by weighing your colorants in grams or pre-mixing your own blends!


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.

Here are the results of my bath bomb color mixes along with ratios and amounts of colorant used.

Green Bath Bomb Color Mix 1

  • Yellow 6:Blue 1 — Ratio 1:1
  • Actual Amount — 1tsp:1tsp
Green Bath Bomb Color Mix 1

Green Bath Bomb Color Mix 2

  • Yellow 5:Blue1 — Ratio 1:2
  • Actual Amount — ½tsp:1 tsp
Green Bath Bomb Color Mix 2

Green Bath Bomb Color Mix 3

  • Yellow 5:Blue1 — Ratio 1:1
  • Actual Amount — 1tsp:1 tsp
Green Bath Bomb Color Mix 3

Green Bath Bomb Color Mix 4

  • Yellow 5:Blue1 — Ratio 2:1
  • Actual Amount — 1tsp:½ tsp
Green Bath Bomb Color Mix 4

Green Bath Bomb Color Mix 5

  • Yellow 5:Blue1 — Ratio 4:1
  • Actual Amount — 1tsp:¼ tsp
Green Bath Bomb Color Mix 5

As you can see, the scale can grow without needing to add lots of color. The Green in Mix 5 has a ratio of 4:1, but that doesn’t mean that I need to add 4 tsp of Yellow 5 and 1 tsp of Blue 1. I scaled it down to just 1 tsp of Yellow 5, and reduced the amount of blue proportionately to ¼ tsp.

Here they all together for comparison.

So, to wrap this up, how did I know that my rainbow bath bombs would have hunter green water as the final color? Look at the breakdown of how I colored them!

  • Red: ½ tsp Red 40, ¼ tsp Red 27
  • Yellow: 2 tsp Yellow 5, ⅛ tsp Yellow 6
  • Green: 1 tsp Yellow 5, ½ tsp Blue 1
  • Blue: 1 tsp Blue 1
  • Purple: 1tsp Blue 1: ¼ tsp Red 27

Now, you can see that the batch total contains:

  • ½  tsp Red 40
  • ½ tsp Red 27
  • ⅛ tsp Yellow 6
  • 3 tsp Yellow 5
  • 2 ½ tsp Blue 1

The majority of the color is Yellow 5 and Blue 1–Green. The dash of Red 27 doesn’t come into play much, and the Red 40, and Yellow 6 will create a slightly darker green, therefore–Hunter Green!

Once you start down this path, you’ll wonder why you ever bothered with pre-mixed colors! What blends will you create?

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!