Howdy clarky,
It could be a number of things.
1. If the spot is v. small, i.e. a single pixel, it sounds like (on a white image) the green pixel of that group of three (RG & B) is dead.
2. If it's larger, like a patch, try moving the focus in and out. If the edges of the spot go in and out of focus, it's probably a dust patch which can be removed with a can of air spray (note, not hairspray
)
3. If it doesn't go in and out of focus then it sounds like a burnt colour filter. In my experience it's the blue one that usually goes, creating a yellow patch, but in this case it seems it would be the green one creating a magenta patch.
If it's new and under warranty they should replace it if it's a burnt filter, and at least clean it if it's a dust spot, but if it's one dead pixel they may try to tell you that it's an acceptable error, although you argue that by being dead centre it warrants a replacement. Hope that helps