Green flickering pixels on Macbook Pro

Issue: Green flashing pixels on black areas of screen.

This manifests itself:

1. 1. On login: around the edge of screen, the whole of the title bar until icons load.
   2. Dark areas when viewing an image on desktop or webpage.
   3. Shutdown: whole of the screen is flashing green pixels.

See attached images.

Device: MacBook Pro (15-inch, Mid 2009).

OSX El Capitan version 10.11.6

Processor: 2.8 GHz Intel Core 2 Duo

Memory: 8 GB 1067 MHz DDR3

Graphics: NVIDIA GeForce 9400M 256 MB

What I have tried:

1) Initial call to Apple: suggested reinstall macOS to prove it's not software issue.

This in itself was problematic as the reinstall function via Recovery seemed to download the OS but the installer would not start. Just returned to Recovery screen.

Then tried to create a bootable installer to USB. Downloaded the InstallMacOSX.dmg ok, but when running the command in Terminal to create the install but the command fails with command not found.

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

2) Contacted apple support again.

They suggested:

a) Start up in Safe Mode.

b) Restart in normal mode.

c) Reset the SMC.

d) Reset NVRam.

None of the above made a difference.

Does anyone have anyone have any ideas or suggestions what might be causing this?

I realise the age of the laptop is not in it's favour, but before I look to replace it just thought I see if the apple Community had a ideas or if it is cost effective to try and fix it.

Thank you for your assistance.