Layers > PixelSquid object > Shadows
The shadow for the PixelSquid PSD is completely independent from the Subject and Background. The shadow structure itself is placed in the layer mask of the shadow Solid Color layer, which makes designating a specific shadow color as simple as double-clicking the solid. Also note that the Shadows layer is not occluded by the object itself. This lets you move the object independently of its shadow without having to painstakingly reconstruct any gaps in the shadow.