Indifferent can also mean
the use of colour in other parts of the poem other than the colour of skin lessens the importance of colour alround, so the author is trying to get you think about racisum without thinking colour.
Lady thinks she will know who he is and more about him if she knows what colour he is, Although the poets many refrences to colour sugests that he thinks there is more to racisum than the colour of skin because he uses colour so much it takes away the importance it therefore shoing there is more to racisum than colour
The lady draws out the conversation even though both know that she will not sell because he is black
shows the type of relationship between a white and a black person, landlady is rude and obnoxious just because he is black
shows formed images are not necesarily true, landlady is not the proper smart perfect person the formed images make whites out to be, the affrican is not the dumb non deserving disgusting person images formed make blacks seem