You have a good beginning, and that is sometimes the hardest part. Consider who this person is. What is it that he is practicing? Why can't he say the words when the time comes? Is he nervous? Is there someone in the crowd making him nervous? Did he write the piece and he's nervous to perform it? These questions will allow you to build a character and plot around this beginning.
I am not sure how you get far in this work without a discussion of what it means to be a woman of color. I would think that this is where your thesis has to emerge. There can be many variations on this, but McMillan focuses a great deal of her energy on articulating the condition of women of color in the modern setting. This might take the form of how women of color deal with additional challenges and barriers that men of color do not have to address. This might come in the form of the argument that McMillan makes that African American men who wish to be successful believe that they need a wife who is white, and not one who is of color. Another potential thesis could be to examine which condition is one upon which McMillan places more primacy in the narrative: Being a woman or being African- American? I think that it might be interesting to examine which one, if there is a choice, does McMillan believes plays a more pressing role in defining the condition of her protagonists. At some level, a choice between gender and race is made and examining where that choice is distilled could make for some worthwhile writing.