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

Certain words in the poem which are in capital letters are: “HOW DARK?', 'ARE YOU LIGHT?', 'OR VERY DARK?', ' OR VERY LIGHT?'

These words exemplify the purpose of the poem which is to showcase the racist mentality of the fair-skinned. When a landlady talks to a tenant, the only matter of concern should be whether the person is suitable for staying with respect to his behaviour, financial position, etc. and not on his skin colour. These capital letters magnify the fact that it is more important for the landlady to know how dark-skinned the person on the other side of the phone is, rather than how erudite or intellectual or well-behaved he might be.