Painting the tanks is not recommended, as gasoline permeates and causes bubbles to form in the paint and decals.
Plastic fuel tanks for vehicles, including original ones, are manufactured using plastic material specifically designed for holding fuel, and these are already produced in the desired color.
For rallies and long expeditions, for example, decals with micro-perforations are applied, which allow the gasoline to permeate, extending the decal's lifespan and preventing detachment.
This characteristic is not exclusive to Gilimoto tanks; it also occurs in original tanks.