In 2002, as a result of an analysis ofalyzing the brightness of 200000 galaxies, some American scientists of thefrom John Hopkins University concluded that the colour of the universe was light green, (rather than, according to the popular belief, black with silvery spots).

Adding parentheses here makes it so that you don't have too many commas.

However, some weeks after their announcement to the American Astronomical Society, they admitted a mistake of calculus andthat they had made a calculation mistake and had to explained the universe's colour, in fact, was a dark shade of brown-grey.

Since the 1600s, some of the best minds have asked themselves the reason why the night sky is black.

StillEven now, no one has found an acceptable answer to this question.

Maybe there isare a finite number of stars or maybe the light of the fuartherst stars hasn’t yet reached the Earth.

The Olbers’ idea was that, in the past, not every star was shineing: something would turnilluminated them on later.

https://www.merriam-webster.com/dictionary/illuminate

What’s Color Is The Universe?

"what color" = "which color" (either of which would be correct)
"what's color" = "the color of what" (which doesn't make sense here)

In 2002, as a result of an analysis of the brightness of 200,000 galaxies, some American scientists of thefrom John Hopkins University concluded that the colour of the universe was light green, rather than, according to the popular belief, black with silvery spots, as popularly believed.

However, some weeks after the announcement to the American Astronomical Society, they admitted a mistake ofin calculusation and explained that the universe's colour, in fact, was a dark shade of brown-ish grey.

According to this article, the color is beige, which is much lighter than brownish grey.

https://www.newscientist.com/article/dn2013-the-universe-is-not-turquoise-its-beige/

Since the 1600s, some of the best minds have asked themselves the reason why the night sky is black.

This question is known as Olbers’ paradox and its name derives from the German astronomer Heinrich Olbers, who described ithis phenomenon in 1826.

A paradox is not really a phenomenon, so I just replaced "this phenomenon" with "it".

Still nNo one has yet found an acceptable answer to this question.

The Olbers’ idea was that, in the past, not every star shione: something would turn them on later.

"The Olbers' idea" suggests that there are multiple people named Olbers (such as siblings or a married couple), and that the idea belongs to both of them.

What’s Color Is The Universe?

However, some weeks after the announcement to the American Astronomical Society, they admitted a mistake of calculusthere was a calculus mistake of and explained the universe's colour, in fact, was a dark shade of brown-grey.

Stay consistent with which spelling of color/colour you use.

The Olbers’ idea was that, in the past, not every star shione: something would turn them on later.