Help my screen is blank

Hello, hi all

OKye i know this has been posted alot before but i need help with this.
okey i have changed cables and monitors for my pc but the screen remains blank. It turns on and everything but nothing showsup on the screen just remains black. the wierd thing is when i plug the screen in the light goes green or fades red depending on the monitor i use.


im thinking it maybe a connection problem and was wondering how i can disconnect the monitor port in the case and plug a new one in,to see if that may work.
my pc is 4 or 5 years old. yes i know its old and i need and upgrade lol. But it was working 100% untill this happened.

one thing that did happen was that when i was playing World of Warcraft on my pc and pressed the windows key the background was green. I have loaded all the data i had with my pc aswell to see if it would help but it didn't.
has my graphics hardware crashed?

so if anyone can help me that would be amezing thank you!