screen refresh rate

Hi all,
just wondering how to go about changing the screen refresh rate on my Dell laptop because once it has been running for about 5-10 mins the screen starts to turn a sort of translucent pixilated pink. As far as I have seen the answer has not yet been posted on this forum. I'm running a dual boot windows 10 and Zorin os ultimate. I have tried the command lines with xrandr and compiz config and none of them seem to work. I am not a particularly tech-savvy person, but I'm fairly certain it's the refresh rate because I had the same problem in windows until I changed the refresh rate from 60 to 40 Hz. any advice would be much appreciated.

Hi

hardware failure? what graphics card does your PC have?

just read here if you have overlooked something in using xrandr
viewtopic.php?f=5&t=13594

+++

I have an Intel HD graphics card. Yes, I did come across that post, and I ran the command

"sudo xrandr --newmode "1366x768_40.00" 85.50 1366 1440 1584 1792 768 771 777 795 +hsync +vsync"

and the terminal emulator's response was

"X Error of failed request: BadName (named color or font does not exist)
Major opcode of failed request: 140 (RANDR)
Minor opcode of failed request: 16 (RRCreateMode)
Serial number of failed request: 42
Current serial number in output stream: 42"

....can someone help me interpret that?

Firstly, are you using an external monitor in addition to the Notebook screen? xrandr is really for 2 screen pc configurations.

What are the results of this command please?:

Code:

lspci -vnn | grep VGA -A 12