My MacBook screen is dark blue with the ball of doom what do I do.

I was using my MacBook Pro 4GB RAM using 10.5.7 (OSX) and it suddenly froze. Scared, I force shut it down by pressing the button in the top right corner of the lower part of the MacBook Pro. It did not seem to be doing anything so I closed the screen. A few minutes later I opened it back up and the screen turned a light blue then dark blue. There was also the loading ball of doom. I could not move the loading ball. Whenever I try to close the screen the light on the side of the Mac facing towards you is off. But when the dark blue screen is on its off as well. I am really confused I don't know what to do. Any suggestions?