For the sorting colors, it's already fixed.
For the output, please mention the language. I'm closing this for the lack of details. You're welcome to raise a new suggestion with more information

If I were to change the rules, I would invalidate the solutions of 211 codewarriors. If you want to play a game, you have to accept the rules... Sorry for that!

Almost 40 Codewarriors succeeded in C# without problems so it can't be an issue for the kata.
It can be a Codewars site error, it happens when too busy.

You pass into my function a list of categories. And there is a requirement to return collection with category->count (event if count is zero). I must add a special condition to meet with requirement 'when books are empty return empty collection'.
So I suggest you to remove this requirement. If list of books is empty then we must return collection with all specified categories (and count = 0)

for c# running tests or submitting gives "unexpected eof" while the code runs just fine (including type of return) in real IDE.