I’m not sure why you’d need or want a randomised controlled trial to determine the colour of the sky. There have been empirical studies done to determine the colour and the reasoning for it - https://acp.copernicus.org/articles/23/14829/2023/acp-23-148... is an interesting read.

I can see it, it's independently verifiable by others, and it's measurable

If you point a spectrometer at the sky during the day in non-cloudy conditions you will observe readings peaking in the roughly 450-495 nanometers range, which crazily enough, is the definition of the colour blue [0]!

Then you can research Rayleigh scattering, of which consists of a large body of academic research not just confirming that the sky is blue, but also why.

But hey, if you want to claim the sky is red because you feel like it is, go ahead. Most people won't take you seriously just like they don't take similar claims about AI seriously.

[0] https://scied.ucar.edu/image/wavelength-blue-and-red-light-i...