Expected behavior:

Pasting e.g. "foo§6bar" into a book results in the text "foobar" being inserted into the book with "bar" formatted with a color.

Actual behavior:

Pasting "foo§6bar" ignores the formatting code "§6" in the middle completely, resulting in just the text "foobar" without any formatting.

It seems that complete formatting codes cannot be pasted into books at all. Instead, every formatting code must be entered manually by first pasting in the section sign (or any string ending with it) and then manually typing the second character.

The expected behavior worked correctly in release 1.13.2, but was broken in snapshot 18w43a.