Combine two vertex color layers?

Question

This one is still version 2.79. I would like to combine the two vertex color layers into one. These are what the layers look like:

I want to add them onto each other.

Answer 1

Not sure this is the best way, but you could try using the Data Transfer modifier (https://docs.blender.org/manual/en/2.79/modeling/modifiers/modify/data_transfer.html?highlight=vertex%20color). Note that I only tried this on 2.83, but according to the documentation you should be able to do this in 2.79.

Say that you have two vertex color layers named color A and color B

1. Duplicate your object
2. On the duplicated object remove color A and rename color B to color A
3. On the duplicated object add Data Transfer modifier. Set target to original object. Check Face Corner Data with Topology method. Select VCol and select color A layer. Set Mix Method to Add

My test: Leftmost sphere with color A layer; Middle spehere with color B layer; Rightmost sphere with added layers.

Answer 2

In 2.79 this is simple:

1. Set Bake Mode to Full Render
2. Set Bake to Vertex Colors
3. In Render tab, disable "Textures" in the Shading category
4. Make sure you have the camera icon set on your target (merged) vcols layer
5. Do Bake