Well, this sounds like the green is dead, but I'm not sure why it is not purple in the white screen. I haven't tried any myself, but I've heard of programs which change the pixel color rapidly to try to recover it. This might help.
I will take a try.
It is really small a pixel on 24" and in my instance the pixel is also in a zone that i don't use a lot.. it is just some centimeters up the windows clock.. but it is annoying know that it exist