Certain words in the poem are in capital letters—why?

Words in the poem which are in capital letters are as follows:

HOW DARK? , ARE YOU LIGHT? , OR VERY DARK? , OR VERY LIGHT?

These words basically highlight the main idea of the poem which is on colour discrimination. These words are spoken by a landlady to a poet; she was putting emphasis on his skin colour when she got to know that he was an African. This shows the mindset of people who are of fair complexion. Landlady was actually trying to know about his tenant complexion so she was putting efforts to know his appearance and these efforts are highlighted by poet in capital words.