Race: C.S. Lewis' Portrayal of Narnia and Calormen

Analyze CS Lewis' portrayal of Calormen and Narnia, focusing on the fact that the Calormenes are the only people of colour in that world. There seems to be a fair bit of racism (and seemingly some references to Islamophobia) in the way he writes the characters from Calormen.
Since 'The Horse and His Boy' is set almost entirely in Calormen and has Narnians and Calormenes directly interacting with each other (Susan and Edmund visiting Tashbaan, Shasta's identity as a Narnian/Archenlander who grew up in Calormen, etc.), it would likely be one of the main focuses. In terms of religion/spirituality, The Last Battle has the conflict of the two 'gods' of the two countries, Tash and Aslan.