The Swiss Airforce acquired quite a few second hand machines from the USAF in 1948. Most of them came in with a so called wing-line painted on their wings. (dive bombing??) Does somebody has further information, photographs for reference?
These straight lines called "Ziellinien" were applied on top of the wings from 1950 onwards. Some aircraft originally had angled lines that aided the pilot to hit the target on low level bombing missions. These were duly replaced with the straight version. It seems that most of these strips were of black but as you may notice in the last picture below these could be of white if a P-51 was of the green camouflage.