2. You mentioned some shippers already agreed to switch to clear plastic whereas others still refuse.
My concern changing clear plastic can solve the colour issue but what type of plastic material they use?
Please check the melting point of the plastic not > 109C otherwise any broken piece difficult to spot if stick to rubber.
As far as I know tarpaulin or canvass sheet can be made from PE , PVC with high melting point between 140 – 160 C, Cotton canvass sheet (Waterproof type)
Coloured material more advisable in case of broken pieces can be spotted and remove.