Green-sensitive opsin is a protein that in humans is encoded by the OPN1MW gene. The number of genes that code for green-sensitive opsin varies from person to person, but in the reference genome (GRCh38) there are three: OPN1MW, OPN1MW2 and OPN1MW3, all which code for identical proteins.
The OPN1MW gene provides instructions for making an opsin pigment that is more sensitive to light in the middle of the visible spectrum (yellow/green light).
See also Opsin OPN1LW OPN1SW
References
Further reading
External links GeneReviews/NIH/NCBI/UW entry on Red-Green Color Vision Defects