imac24" blue and yellow squares

Hi guys , since a couple of weeks i am having this blue and yellow squares on my imac24" , i ve been looking all over the internet for a solution without any succes . I ve tried disk utility , restore harddisk , pixelfix , etc...
You can see some blue squares around the tears above in the image

Is there anybody that can help me ?

Thanks in advance

I'm assuming that's a screenshot you posted? Try attaching an external monitor or TV to the iMac and see if the same blue and yellow squares appear there. If they appear on the external monitor, it's a graphics adapter problem, if not, it's a pixel problem occurring with your internal display.