Change the color of the default (no) material (Cycles)

In the idea of having a faster workflow, I would like to know if it is possible to change the color of the default (no) material of Cycles. I mean, if you don't assign an material to an object, it is by default a diffuse material that is light grey (0.8 white).

I like to have my objects having that default light grey because then I can give certain meshes more emphasis simply by assigning them a pure white material; which give the scene some contrast.

How could I change the color of that default light grey so I could darken it and accentuate the contrast ?

The idea being to be able to do this using no materials (default color), because assigning ALL meshes a material would be too long in my work process.

Actually I use a light to make my subject more bright. But this has a lot of inconvenients, that is why I ask !

Thanks!

• The default material is hardcoded as far as I can tell. "Because assigning ALL meshes a material would be too long" Select all Ctrl+L> Link Materials. How is that too long? you then get all the control you like – Duarte Farrajota Ramos Jul 5 '18 at 23:40
• You would need to build your own custom build of blender to change what blender uses when there are no materials. Setting the material override in render layers is a way to use one material for everything. – sambler Jul 6 '18 at 6:06
• @DuarteFarrajotaRamos thanks for those precisions. Is it possible to better select all meshes that don't have any materials set ? – gordie Jul 6 '18 at 7:07