Sorry, no such thing as a "black sun"
...or any kind of sun that can bleach out all colors of the magnetic spectrum. It's one thing to use color (or black and white) for artistic reasons (creates good symbolism in visual story-telling), but frankly, there literally is no such thing as a star that can give off visible light that the human eye can detect that will bleach out all colors except black and white.
I've seen environments on earth that almost seem devoid of color, such as empty wastelands in central Asia, deserts, arctic areas where the snow has melted, very large, heavily abused mining pits in central and eastern Russia, and volcanic aftermath. But even in those places, there's always a little bit of color, even if it's nothing more than the blue sky above, or someone wearing a brightly colored piece of clothing, or a single, small, green plant poking out of the ground.
It would have made more sense to have Geidi Prime with that setup than using fake fantasy sci-fi to try and make an already unlikeable enemy strongold even nastier to look at.