This is the problem. In Vue you can only get black shadows(no colour info). This is wrong, if you can play with the colour of the light you should be able to tweak the shadows as well. I need a solution for this, but not one for a single object but for complex ecosystems and scenes.
Also, I do not want to multipass and then composite, but to be able to see in preview renderings(and so have speed and versatility) what I am changing.
Unfortunatelly I can't think of a way and don't even think one exists. What I mainly want besides suggestions is to make people interested in this missing feature and get their support.