colored translucent shadows used to be/are capable with static lighting: Using Colored Translucent Shadows in Unreal Engine | Unreal Engine 5.0 Documentation
But Lumen doesn’t use lightmaps and therefore static lights do nothing, so colored translucent shadows likewise don’t show. Is there some other way to produce colored translucent shadows? I would think that this would be a graphical effect that can benefit significantly from Lumen and raytracing, so perhaps in the future it could be implemented.
As an aside, I think implementing it wouldn’t be too difficult from a technical point either. Generally shadows are created because the shaders didn’t apply light calculations to a surface based on a depth map relative to the light source. Translucent materials simply either act as a surface that shows in the depth map, or they don’t depending on if shadow casting is on for the material. For colored translucent shadows, I think just one additional pass per surface would be needed- when a light hits a translucent surface, after calculating lighting for that specific surface, lighting would be recalculated as if the surface were removed, but only on that surface area, and the light would have different properties based on how light changes as it goes thru a colored surface. In theory it sounds simple but UE is very dependent on shader compilation and doing something like this would involve being able to recursively call functions and recalculate texture maps in realtime, something GPUs don’t do well (however raytracing is also a recursive procedure so this might work best if it were an extension of ray calculations).