A few species communicate with sound. For example, the male Cracker Butterfly can produce noises with its wings. Each scale is a single color, most of which are produced by pigments. The iridescence that's sometimes seen is produced from a reflective microstructure on the surface of the scales. Most insects have a larval stage known as a 'grub', with six legs.
Some caterpillars turn into butterflies, but most turn into moths.
Caterpillars have the 6 legs of other insects, plus up to ten 'prolegs' that distinguish them as the grubs of moths or butterflies. The 6 true legs are jointed, with a little claw on the end of each. Prologs are cylindrical, not jointed, with a tiny hook that makes them good for walking or clinging. The 6 true legs on the thorax remain throughout pupation, and these become the legs of the adult butterfly or moth. The prolegs disappear.