What is the ruling on coloring bad images and drawings found in a borrowed book with a scientific concept, knowing that the coloring will not affect the book's content or benefit from it, or must it be returned as is because it is the property of others?

The presence of images in scientific books may be important for specialists, such as in medical books, so they should not be immediately erased. If they are not essential, they should not be erased unless one is certain that a greater harm will not result. The duty is to advise the owner of the book.