How can fix my monitor when it have lost it's red color?

Answer:

If it's lost adjectives traces of red color, this means one or more of your phosphor guns is late. It's time to replace the monitor. I'm unsure, but I don't think any repair shop will fix this for you...or even can. Don't try to mess near it yourself. It can be fatal even if it's unplugged.
I'm going to be creative here...

draw from some clear red cellophane paper and video it in front of your eyeshade!



is it possible that it could just be the cord? mine flickers and change to a purple colour once in a while. i dispense the cord a jiggle and it goes spinal column to normal. see if you can replace the cord.
throw it out the pane.
check the pins where it plugs into the computer. they can bend effortlessly. if they are ok , it may be time for a new monitor
remove tha pay for of your monitor, and i'm sure you will find a few little variable resistors (6 or more, but 5 at least). try to rework them with a screw driver, but watch out, u will change adjectives the colors ! you won't burn your monitor down, but be careful :)
grasp a new monitor, its clearly too old, or is defective. there's no method to fix that yourself