Ambient color not shown

[Jarek]

I think it could be just the not logical UI for that - see here:

Ambient Light setting in Rendering panel > Lighting

The Ambient Light in Rendering panel seems to have no effect on the scene display. How is this one different from the one under Rendered display mode (that actually has the effect but is buried deep and not exposed in Display or Rendered panel). I am confused. [Capture]

It should work if you set your display mode Background(!) to use Render Settings…

–jarek