Combining multiple textures with a white background I'd like to sort of "overlay" these shaders, but the only options are mix and add. Allow me to explain.

I made two images, both white background, one with red scribbles and one with blue scribbles, both 1920x1080. Image textures plugged into diffuse was my node setup. I want both scribbles to be added to the plane while the background stays the same color.

If I mix them I get the following:

The red and blue scribbles are now 50% dimmer than they would be on their own, and the white color hasn't changed in intensity.

If I add them I get the following:

The red and blue scribbles are still 50% dimmer than they normally would be (since the white background is being added over each). But the white background is now 2x brighter than normal.

Can I get a result where the white background is normal brightness and both the blue and red scribbles are at normal brightness?
Here's an example with two images with a white background:

To keep the white and mix the two colors you can use a Color MixRGB node with Multiply as the transfer mode. Then plug that to only one Diffuse BSDF shader:


Using Multiply as the transfer mode (quoting from the wiki)

Returns a darker result than either pixel in most cases (except one of them &gt;equals white=1.0). Completely white layers do not change the background at all. &gt;Completely black layers give a black result. The &quot;opposite&quot; to Screen mode.

More info here