Squid can communicate with each other without any other fish noticing:

Squid and their relatives have eyes that are sensitive to polarised light and to them and are known to use it to signal to one another. Their predators on the other hand, like seals or whales, don't share this ability and cannot see the squids' signals.

Most of all, the polarised iridescent light, is not affected by the chromatophores and passes through unaltered. This means that camouflaged squid can have entire visual conversations while remaining invisible to passing predators. In the world of squid, conversations carry secrets wrapped in lies.