versicolor is caused by a fungus that lives in the skin of almost all adults. Factors that can cause the fungus to become more visible include high humidity and immune or hormone abnormalities. Treatment involves topical and oral antifungal medicines. Instead of selsun blue, use selsun shampoo and if the symptoms persist then please consult a dermatologist as oral antifungal drugs may be needed.
I hope it helps. Take care and please do keep me posted in case you have any additional doubts. Kind regards.