I would like to paint my textures with 100% on my terrain but as it seems that is not possible? The base layers always manipulate the higher layers and that mostly by luminance. If you make the base layer white all higher layers will become bright grey no matter the color they have:
As you can see the base dirt color is set to white and the grass color set to red, yet you can see on the left in layer previews that it all goes white.
I assume it is some trickery in UE4 to reduce texture information needed to blend those layers into another.
The main problem I currently have is that I want to paint the same grass on the terrain that I have on a mesh that I place in the world. So I want the terrain grass to match my grass on a object but that seems rather impossible since I always also have to tweak all underlying layers to somehow match it.