I found this on another site:
25. I have trouble playing blue PS2 games. What can I do to fix this?
1. Apparently, blue PS2 discs are lighter than then silver ones, so they tend to move around more when the PS2 is reading it. To fix this, you should put tape on the top of the disc. This will make it heavier, so it won't move around too much and it should make reading the disc easier for your poor PS2. Don't go overboard with the tape though.
2. If the problems occurs when the PS2 is horizontal, try putting it into its vertical position. Or try putting it horizontal if it is vertical.
3. Use a can of compressed air to clean dust out of the system.
4. Send your system to Sony for repairs.