Okay, so I am more involved with safety than I am quality at this point (former safety czar turned quality supervisor guy) so my buzzers are going off big time here from that standpoint. I'll try to suppress that. I sense that this CB is trying to achieve the same results my safety auditor would
(we had a few accidents leading to a pretty serious one, i saved my company out of some issues and now am being positioned to do the same with ISO).
So, in your case any satellite container MUST be labeled, no excuses. I purposely buy open top containers, and spend a small fortune on them. Any clean containers that are not labeled need to be stored in the fire cabinet where there are respective locations. We do toolbox talks with gathered signatures for our safety program that trains procedure for that. Process is kept in the safety handbook, policy as well. I'd say this is a safety issue handled by a safety team rather than an ISO finding.
However, if you use the wrong materials for any job its an issue. I'm new here so be gentle and take it with a grain of salt.