Thanks!!
The main shadows (bottles and solid ingredients) are just done with Unity's lighting system, with shadow quality bumped way up.
As for the colored liquid shadows, I actually had to cheat a little, using several colored spotlights with spot angle, color, and intensity set just right. The bottles are invisible 3D models that cast shadows, with a bunch of invisible sphere colliders inside of them. The spheres act as a very rough, first-order approximation of a liquid, so when you shake the bottle the spheres slosh around, roughly like a liquid would. If you then track those spheres with spotlights as they move around, it makes for something that looks like the shadow of a transparent liquid. But if you take the spotlights and point them at a random sphere every frame, it gives a shimmering quality to that liquid-shadow!
As my own harshest critic, I have to say that it looks a lot more convincing when the number of spotlights is close to the number of spheres in the bottle. In editor, I was using between 50 and 100 lights to point at 100 to 200 spheres, but WebGL restrictions made me cut down to just 7 lights for the same number of spheres. But all-in-all I'm happy with how it turned out :)