The military thought this paint job could protect from nuclear blasts
In the 1950s, America's nuclear bomber pilots had a very valid concern about firing their weapons. In many cases, an aircrew that fired a nuclear weapon would be hard-pressed to outrun the blast when the warhead detonated.
To reduce the problem, the Air Force adopted a new paint scheme for many bombers. It was thought that the bright, "anti-flash white" paint would reflect a portion of the thermal blast from the bomb. The idea might sound funny, but a test from 1953 backs up the idea.
Operation Upshot-Knothole was a series of nuclear tests in Nevada. In the detonation named "Encore," a group of three homes were tested against a 27-kt nuclear warhead. One house had old paint and trash in the yard, one house had new paint and trash in the yard, and a third house had new paint and no trash. In the test, the trash set on fire and burned down the first home. The second house experienced small fires on its most weathered areas that eventually grew and consumed the house. The third structure, with new paint and no trash, was scorched but survived the test.
"Anti-flash white" and "anti-atom white" began showing up on bombers in American, allied, and Soviet arsenals in the mid-1950s. The white paint provided decent camouflage when viewed from below, but some governments painted the tops of the aircraft with other colors since an all-white aircraft flying over green or brown terrain would be easily spotted from above.
Eventually, the need for stealth coatings became more important than reflecting thermal radiation. Modern nuclear bombers have advanced coatings to ensure a minimal radar signature.