I'd probably shine an array of narrow-beam LEDs through a sheet of aerogel. (the aerogel disperses the blue light) If the LEDs are on long horizontal rods that can rotate, that lets the angle change. You'd need the beams focused down to about half a degree, with at least a dozen viewed in a circle of that size from the perspective of a tall person under the light.

Another way is just an RGB array, with different lenses on the different colors. The blue gets a fish-eye lens, while the green and red get focused down to about half a degree. Again there can be rods that rotate, and at least a dozen LEDs need to be in a circle of half a degree when viewed by a tall person under the light.