Move the Sun: watch scattering colour the sky and the Sun

Sun height above the horizon: 60°

No atmosphere (like the Moon)

Air the light crosses	–
Blue reaching you directly	–
Red reaching you directly	–

Simplified model: three colours (450, 550, 650 nm), Rayleigh scattering by air only (∝ 1/λ⁴), single scattering; dust, haze and clouds are left out.