My particular knowledge of dramatic literature is rather limited to those works that have been used in opera. There is probably no definite answer to your question, but maybe analyses of a few esamples can be of help. For instance, off the top of my head I could recall at least three to four operas that deal with some kind of colonialism, or perhaps (should be said) independence or liberation from colonialism: Guillaume Tell (by Gioacchino Rossini); Aïda (by Giuseppe Verdi); Lo Schiavo (by Antonio Carlos Gomes); Bug-Jargal (by José Cândido da Gama Malcher). Perhaps some interesting facts can be said about them. In Guillaume Tell, the main (homonymous) character that works towards the liberation of the Swiss region is a noble who is raised (unwillingly) to the position of representative of that liberation, but his role is also contested by the people (choir) who wonder if he won't just become another despot. A similar situation occurs with main (homonymous) character in Burg-Jurgal, but deals with the independence and slave revolt in Haiti (the first slave revolt and liberation of slaves in the Americas, although the composer is Brazilian). Another Brazilian composer (Carlos Gomes), intended to do an opera on black slavery, but due to censorship he ended up doing an opera dealing with Brazilian Native Slaves, in line with a reversed Disney-Pochahontas tale (the Indian male slave falls in love with a Portuguese female noble). This kind of love story is also the foreground for Aïda, in which the homonymous main female character is an Ethiopian slave in Egypt, but falls in love with the Egytian general (Radames), who reciprocates — at that time (end of 19th century), Italy help claim over the nearby (and rebellious) colony of Eritrea.
Please, let me know if this is vaguely in line with what you intended with your question (although I have not information about Nigerian texts or opera).
Frantz Omar Fanon was a psychiatrist, philosopher, revolutionary, and writer whose works play a crucial role in the fields of post-colonial studies, critical theory, and Marxism. In point of fact, Fanon , as a political radical, Pan-Africanist, and Marxist humanist was greatly concerned with the psychopathology of colonization as well as socio-cultural consequences of decolonization.He ardently supported the Algerian War of Independence from France, and for more than five decades, the life and works of Frantz Fanon have inspired national liberation movements and other radical political organizations throughout the world . His works have a leading role in post-colonial discourse due to the unique nature of his ideology and originality of his thought and the enlightenment underlying his criticisms.His rigorous social existential analysis and interpretation of anti-black racial tendencies , helped him to unravel the factors dominating the micro/ macro semiotic structures in post-colonial discourses of the modern era.
As such, dramatic literature addressing post colonial themes are mostly manifested through post-independence drama, play and theater. More specifically, post colonial dramatic literature creates specific dramatic and theatrical contexts which reflect the sociopolitical conditions of particular post-colonial regions. As an illustration, Shakespeare's work " The Tempest" helps the audience understand facts related to French colonialism in the Caribbean region. For more information< I refer you to the following links, which hopefully satisfy the question.
To my personal mind (which is, certainly, disputable), dramatic literature that touched upon the postcolonial ideas reached the highest level in the works of my favourite novelist - Flannery O'Connor, who describeв in detail the atmosphere of former planter's south thus helping to form the reader's attitude towards the relations between former slaves and their former masters.
A psot colonial reading of dramatic literature is interesting indeed. Dr. Faustus the classical example. Tempest has another. It is good to analyze the characterization of the natives in Tempest.
I am rather into prose and poetry (Heinrich von Kleist's 1811 narrative "Die Verlobung in St. Domingo") than drama, but I definitely would suggest that you read the article "Of mimicry and man: The ambivalence of colonial discourse" by Homi K. Bhabha (in his book "The Location of Culture", NY, 1994/2004). He read Fanon. Bhabha's texts are very inspiring and will help you in any postcolonial analysis.