@tstoddard - don’t get too caught up in the idea of color models/spaces just yet. It can be counter-intuitive to wrap your head around but at the end of the day the biggest things to keep in mind is

adjusting each channel in the mixer (red, green, or blue) will *only adjust how “bright” ***that** particular color is.

You won’t be adding any other colors into the mix. The channel mixer only let’s you adjust how intense that particular color is.

Hopefully I can clear this up. Let’s consider four “pixels” that are only made up of a **Red** and **Green** channel (we’re ignoring *Blue* for the moment to simplify things) that go from 0 – 255.

From left to right, we are going to set their initial Red, Green values as:

**First**: 127, 0

**Second**: 127, 64

**Third**: 127, 127

**Fourth**: 0, 127

So, let’s look at modifying only the **Red** channel in the channel mixer. I’m going to use GIMP for this example but the theory should be the same everywhere.

So on the **Red** channel, let’s push the *Green* contribution up to “50”.

What I would expect from this is to take the **Green** channel value for each pixel, multiply by 50%, and then add it to the **Red** channel.

###
First Pixel

So let’s look at the **First** “pixel”.

It’s values are R = 127 and G = 0. So…

- Multiply
**Green** channel value by 50%:

0 × 0.50 = **0**
- Add the result to the
**Red** channel value:

127 + 0 = 127

The final result of this operation on the pixel will be nothing:

**R, G = 127, 0**

###
Second Pixel

The second pixel has something interesting finally happening to it.

Remeber, it’s values are R = 127 and G = 64.

- Multiply
**Green** channel value by 50%:

64 × 0.50 = **32**
- Add the result to the
**Red** channel:

127 + 32 = **159**

The final result of this operation on the **Second** pixel will be:

**R, G = 159, 64**

###
Third Pixel

The third pixel has it’s values as R = 127 and G = 127.

- Multiply
**Green** channel value by 50%:

127 × 0.50 = **64**
- Add the result to the
**Red** channel:

127 + 64 = **191**

The final result on the **Third** pixel is:

**R, G = 191, 127**

###
Fourth Pixel

The fourth pixel has no Red in it: R = 0 and G = 127.

- Multiply the
**Green** channel value by 50%:

127 × 0.50 = **64**
- Add the result to the
**Red** channel:

0 + 64 = **64**

The final result on the **Fourth** pixel is:

**R, G = 64, 127**

If we actually do this in GIMP, we see that this is exactly what we get (notice that the **Green** channel hasn’t changed at all in this *only the ***Red** channel).

Top, after channel mixer +50% R(G), bottom original.

If we go further and instead adjust the **Red** channels *Green* contribution, R(G), up to 100%:

**First (R, G)**: 127, 0 ⟹ ( 127 + (0 × 1.00) ), 0 ⟹ **127, 0**

**Second**: 127, 64 ⟹ ( 127 + (64 × 1.00) ), 64 ⟹ **191, 64**

**Third**: 127, 127 ⟹ ( 127 + (127 × 1.00) ), 127 ⟹ **254, 127**

**Fourth**: 0, 127 ⟹ ( 0 + (127 × 1.00) ), 127 ⟹ **127, 127**

Which is what we see when doing the operation in GIMP:

Again, in all cases, notice that the *Green* value *doesn’t change* - we are only modifying the values of the **Red** channel.

Hopefully this makes sense?