I am happy to announce our new extension - Shadow Colour for shadow studies.
Shadow Colour allows you to assign colours to Groups/Component shadows in Sketchup and quickly generate high-quality images and GIFs with coloured shadows.
You can find the extension here.
The user guide is available at this link
It’s great… if you’re made of money / business. Indie users gotta continue to go the manual route. 
There’s a free plugin that creates geometry out of shadows, I don’t remember the name but I watched it on a video of sketchup essentials. It seems to me that it’s overpriced this extension specially having free alternatives, but maybe it’s worthy for someone else.
