Making intersecting parts of objects turn the combined colour? (red+blue=purple) I want to make the intersecting parts of the objects (they are two different objects converted from text) turn the combined colour (a kind of purple, I guess). How could I easily do this, without having to use the knife tool? Could I use materials to do this?

Also, do I have to assign what the combined colour would be, or is there any way to calculate it in Blender?

I tried using the boolean modifier, but it acts very weird, I don't get the desired effect.

I was thinking if there would be a way to separate the intersecting parts from the objects to create new objects where they intersect so that I could turn the new objects the required colour.

The image is from the view port.
You can use Boolean modifiers if you want to have full
   control of the intersecting material.

Starting situation:



These objects must not be touched, as they are the "basis" for the modifiers. So the first step consist in copy the left (or the right) object) and hide all the other. We'll call this "Left copy intersect right"



Add to this object a Boolan modifier, set to "Intersect" an than point to the right object.



Here we have the first part of three... we can assign a purple material to this object.

Copy again the left object, assign boolean modifier an this time set boolean operation to "Difference" and point to right object.

  

Finish with the last part. Copy Right object, add boolean modifier, set to difference, to left the object.

  

Assign material to the three object as you wish



You can use Volume absorbtion shader if you want that the two materials blend themselves for real



Create a material based for example on a glass shader for the surface and a volume absorbtion shader based on wanted color for the volume output.

Notice that these are the "origninal" right and left objects, so you don't need other operations, but you have some limitation on the material... they must have a transparent component.

Also notice (in the 3D view on the top) that you have to move the geometry a bit, to avoid overlapping faces that may cause artifacts.

Here's another possible material and the blendfile: