Transparent but wildly colored candy-apple paint, applied atop a metallic undercoat, and metalflake paint, with aluminum glitter within candy-apple paint, appeared in the 1960s.
These took many coats to produce a brilliant effect – which in hot climates had a tendency to flake off.
Once customizing post-war cars caught on, some of the practices were extended to pre-war cars, which would have been called fendered rods, with more body work done on them.
An alternate rule for disambiguation developed: hot rods had the engine behind the front suspension, while customs had the engine over the front suspension.
A development of hot rodding, the change in name corresponded to the change in the design of the cars being modified.