Which of these does the author use to create certain moods?

It depends whether in a book, movie, or something else. But I am assuming this is for a book.

It is not A, because there are none when reading a book. It might be floating text, but it is most likely not. It can be C if the book has pictures but it may not. That leaves D. Colors can mean 2 things. The actual colors, which is a noun, or colors a verb. The verb makes colors in a paragraph or sentence by using adverbs and adjectives to give life and to make it more interesting to the viewer.