CFR 49 Part 172.322: Marine pollutants
(e) MARINE POLLUTANT mark.MARINE POLLUTANT mark. Effective January 14, 2010 the MARINE POLLUTANT mark must conform to the following:
(e)(1) Except for size, the MARINE POLLUTANT mark must appear as follows: 
Symbol (fish and tree): Black on white or suitable contrasting background.
This is a change from the old labels, so make sure you order some new ones.
CFR 49 §178.703 Marking of IBCs.
a)(1)(vii) (A) The stacking test load in kilograms (kg). For IBCs not designed for stacking, the figure “0” and the symbol for IBCs not capable of being stacked must be displayed. For IBCs designed for stacking, the maximum permitted stacking load applicable when the IBC is in use must be included with the symbol for IBCs capable of being stacked. All IBCs manufactured, repaired or remanufactured after January 1, 2011 must display the applicable symbol as follows:
IBCs NOT capable of being stacked