The orientation of the flakes of metal (or ceramic in the case of pearl finishes) can affect the final finish. When metallic or pearl finish paints are sprayed, these flakes are consistently aligned and the finish reflects light accordingly. When such paints are brushed on, these flakes can lay in the paint differently, causing less light to be reflected. This appears darker. We recommend that you apply another coat (if necessary, polish the existing top coat down a bit to make room for the new coat). Try to brush this coat on lightly. Then polish it, clear it, and polish and wax the clear. That should help reduce this dark effect.