What the literary term that fits this definition dark light?

Answer 1

I don't see that this is really a literary question. Dark light would most usually refer to some wavelength that the human eye does not see, particularly the ultraviolet.

Answer 2

The literary term that fits this definition is "oxymoron," which refers to a figure of speech that combines contradictory or opposing ideas (such as dark and light) to create a specific effect or meaning.