The Carley float was not made of rubber.
The definition I have is:
A life-raft in the form of a large oval ring of canvas painted to make it waterproof and stuffed with kapok or granulated cork, and with a light wooden grid inside the oval and hand lines on the outer circumference.
Most of the photos I have seen show the floats are painted a pale colour usually to match the camouflage of the ship.
With regard to Snowberry all the photos indicate this.
Snowberry also had two different shaped floats as can be seen on my own humble modelling effort.