about my monitor

hello
I am having a problem
with my computer's monitor.
It never displays the true color instead the whole screen is filled with yellow
color. i've tried to adjust it by pressing the user mode buttons on the monitor
in the color choice/"RGB"/the only blue color shows me an effect.but the rest RED & GREEN colors are not available how can I,restore my computer to earlier setting. I've even tried to adjust the color in Display,settings but I couldn't.