Mine Brute is grey in colour and has number 4 as marking it's grade:
#4 – LDPE (Low-Density Polyethylene)
LDPE is often found in shrink wraps, dry cleaner garment bags, squeezable bottles, and the type of plastic bags used to package bread. The plastic grocery bags used in most stores today are made using LDPE plastic. Some clothing and furniture also uses this type of plastic.
LDPE is considered less toxic than other plastics... and so on
Apparently is not design for very long food storage - I would guess it means months - but for few weeks should be OK