If I remember correctly, the color of the band indicated the contents of the barrel...typically, full fuel drums wouldn't be carried by a cargo ship, the liquid would be transported by a tanker to a location overseas where it was off-loaded into storage tanks, then distributed.
If I remember correctly...and it's been awhile...white band indicated water, red indicated solvents, yellow indicated petroleum products (oil, gas).
Don't quote me on that though...
Jeff