Organisms that change colors contain pigments called chromatophores. There are many different kinds of organisms that have chromatophores, including amphibians, cephalopods, bacteria, fish, and reptiles! Two of the kinds of organisms listed are invertebrates: cephalopods (organisms such as octopi) and bacteria. This is an interesting and rich topic. I suggest you go to Wikipedia and look up the "chromatophore" page if you would like more details!

Yes, and much better than a chameleon, in fact: squid, octopus, and cuttlefish all are capable of changing the patterns and colors on their bodies - except that the squid or octopus has thousands of colors and patterns it can assume, while a chameleon has a few tens.