Achieving correct shadows of semi-translucent objects

This is what I want to achieve (Mockup made in Blender):

I have a semi-transparent image on a plane that should cast shadows onto another plane. Those shadows should be tinted corresponding to the translucent color and be stronger where the image-plane has more alpha.

I’ve played around a loot with shadow-settings, material settings etc. To no avail.
How would you approach this problem? Is there something simple I am missing or do I need to do something more custom like projecting with a light, modifying shadowmaps etc.?

This is a minimal example of where I am at the moment. I am a new user, so I couldn’t attach it to the first post directly or post the project file apparently.

Yeah, this is an advanced technique not available in most real-time graphics software, including TouchDesigner. However, you could try to fake it using multiple render passes and a light with a Projector Map setup to simulate the light shining through. Otherwise you could try to write your own GLSL material to achieve this effect.

If physical accuracy or ease of development is important for this project, I’d consider switching to other software.