The upper dimples are blue formation lights. Check a copy of F4U Corsair in Detail and Scale (Vol. 55) - page 42. Don't putty them over! Paint 'em.... well... blue.
Not sure what you are referring to on the lower side. They did add the blue formation lights (same as upper ones) to both lower wings in later versions like the F4U-5, but not on earlier versions.
Also, there are 3 coloured (red, green and amber - front to rear) identification lights, but only on the lower right wing - the left lower wing should be clean as far as the reference shows for versions before the F4U-5 .