Green Tint no longer present on display, everything has red tint

My daughter had changed the background image on her desktop when "something" popped up in the bottom right corner related to color. Whatever she clicked after resulted in the entire screen tinted red. This occurred in not just her user profile but changed every user profile including admin. I've tinkered around with color management and changing calibration and the only thing I see to be able to tell is that the green tint seems to be gone --- I noticed this when adjusting the red/green/blue sliders to eliminate color from the gray boxes in color calibration, where changing the green slider (which seemed black instead of green) did not seem to have any effect whereas the other color sliders were functional. I'm trying to reset it back to normal colors and I'm not having any luck. Any help would be appreciated.

Ranger4,
Thank you for the warm welcome and your response!

As it turns out, my daughter inadvertently and coincidentally knocked loose the video cable...I should have known with the loss of tint. So problem solved!

Embarrassingly enough for me, it was discovered by my wife who knows how to turn a computer on but not much more. I lauded her for trying to fix it with her lack of basic computer knowledge, so now I'm eating my own words and trying to make it up to her tonight.

Thanks again,

Humbled