Currently Octane has not blending. Also you can't use a Octane node under C4D's textures. Because it's converted to textures on cpu. Cpu cannot render octane textures. I'm not sure about plans, but octane team is improving the things as quick as possible. I want also to have this option with many others.
If we could have blending modes on "mix node", we would be able to generate a Custom Layer mode in Octane
Octane For Cinema 4D developer / 3d generalist
3930k / 16gb / 780ti + 1070/1080 / psu 1600w / numerous hw