Cause:
Insufficient amount or film thickness of the color coat.
Colors are not properly mixed.
The color has been over-thinned.
The substrate color was incorrect or uneven.
Prevention:
Use thinner according to the recommended ratio.
Mix the color thoroughly.
Use the appropriate primer.
Polish or use proper polishing techniques.
Correction: Apply a sufficient amount of paint until full coverage is achieved, or sand and repaint.