I thought about this when I came across wiens displacement law which says the higher the temperature, the lower the peak wavelength. If the sun was a lot hotter, and its peak wavelength wasn't in the visible part of the EM spectrum. How would this change the suns appearance to us?
If the sun's surface would be hotter, then - instead of being white - it would look more bluish-white.
Even if it would be much hotter, and the spectral peak would be in far ultra-violet, then the visible part of the spectrum still would make it look bluish for our eyes.
This graphic from Wikipedia: Color temperature visualizes how the color of a Planckian light source depends on its temperature $T$.