Phosphenes are colour patterns and shapes that do not enter the eye in the normal way, but are instead produced within the eye and brain. Ever see stars? They were phosphenes.
Dr Max Knoll very helpfully grouped phosphenes into 15 different categories, although he did this by using electrical induction on test patients, so you might want to check how humane his methods were before metaphorically patting him on the back (he died in 1969). I'm sure it was fine.