My ps2 plays only the discs that have a blue

Your lens could require cleaning or replacement.

If you're using the original PS2 model, use a laser lens cleaning disc.

If you're using the slimline PS2 model, get a cotton swab and some non abrasive alcohol, isopropyl alcohol works particularly well as it's completely safe for electronic devices such as these, and dries quickly.

If after cleaning your games will still not play, your laser may need replacement. If you are not comfortable with replacing the laser yourself, charge someone to do it for you, or replace the system entirely.