Dead pixels? or something else?

hello everyone. Ive been having issues with my mac lately. I have attached some screenshots of my desktop. At first i believed these were dead pixels but it seems not to be, the reason why i think it is something else is because when mirroring my screen on something like chrome cast this discoloration still is on the mirrored screen. Now this new thing just recently appeared, it is the same "dead pixel"but this one follows my mouse around. The pixels also tend to smear when you drag a window into them.. Any tips and advice would be appreciated,
Thanks!

Thermonuclear said:

Periodically positioned graphic irregularities is usually a sign of defective video RAM and can be caused by overheating.

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I recently had my hard drive replaced, while doing this they boosted my ram, my computer has been overheating lately. Will reducing the ram solve the problem?

johnf1285 said:

something is going on with your gpu. Did you have any information on what year and what specs your machine has?

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DeltaMac said:

Seems unlikely that reducing the RAM will help with the overheating.
Better to find out what is causing the overheating. You need to find out if the fan(s) is running when needed. SMCFanControl utility will help you out with that. http://www.macupdate.com/app/mac/23049/smcfancontrol

There's various utilities that can reveal the actual reported temp sensors output.

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this app is really helping! my computer has always had a heat problem. Now if i replace the ram will the graphic discolorations go away?

DeltaMac said:

I think you could install more RAM. Your iMac can have up to 6GB installed.

However -
It's not too likely that adding more system memory will help your video artifacts, which may simply be the Radeon HD 2600 PRO showing its flaws.

If the fan utility helps your video by keeping the temps under control, then that's a good thing…

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so a new graphics card may be necessary?