vertical lines

I have a 2 year and 2 months imac. 15 days a purple line appeared,
later a yellow and today a blue one. So, I suppose more will be
coming. I've searched the Internet and I see this is a common issue,
but all I do is surf among different forums with questions and no
answers. What's the solution to this problem, whichi si obviously
apple's fault?

I live in Spain and the serial starts with CK61... of course my
warranty after 2 years and 2 months is over.

Thanks!