According to Hemmings Motor News, an old truck with original paint is more valuable than one that has been repainted. According to CarsDirect.com, however, paint is not one of the factors that affect classic car pricing. CarsDirect does take into account the condition, including paint, but not necessarily original paint.
There are a number of reasons why original paint can help the cost of a classic truck and a few reasons why the original paint doesn't matter. Authentic, unrestored old trucks and cars have more value when they have the original paint because it's part of the original make of the vehicle. It also proves that the vehicle has not been mishandled or in an accident. Even though the original paint can make the old truck worth more money, it is hard to prove that an old truck has not been repainted. Because of this, not all old car pricing takes the paint into account.