Problem with the Power Supply

Hello to everyone on this forum. I had a problem with my computer the past 2 weeks where I would press my power button and the computer wouldn't boot. At first i thought it might be a problem with the power button of my case(I had the 650D and I knew about it before i got it). So i removed the key in order to press the button directly. Then the pc wouldn't start even then or(!) if it would it would do so after a couple of minutes(3-6 min). I didn't want to jump into conclusions so I took my side panel off i removed the power pins and later tried to start the computer with a screw driver(of course after I would turn it off from the PSU). Still it wouldn't start or if it would it would do so after some time. The leds on my motherboard are all working fine so there was no problem there. What I did also notice is when i was playing a game the graphics would be more darker(like the blue color would be more dark close to purple). I asked a friend of mine for an advice and he told me that my graphics card is probably not getting enough power from the PSU which was my first fear. So after testing all that should I send it back for a warranty?(I got the rig for 5 years and the PSU is the ATX860).

Thanks in advance.