Description of problem:  
    The old paint or the ground coat is visible underneath the  topcoat.

Causes:         
    – Paint was not stirred well.
    – Paint is over thinned.
    – Thinner is too slow which makes the paint run before the required thickness
       is achieved.
    – Thinner used is incorrect.
    – Not enough spray passes (too low film build).

Preventive measures:
    – Stir the paint well.
    – Use appropriate thinning ratio.
    – Use appropriate thinner.
    – Spray sufficient topcoat to obtain opacity.

Remedy:
    Allow drying fully.  Sand and repaint.