The Kelp Chips bag is light blue in color. On the front, there is a dark-green circle with the chips' name written in capitals and a yellow font inside it. They are likely made of kelp, given the name.
Role in episode
Plankton eats a bag of Kelp Chips while watching TV in the Chum Bucket. They are seen on a couch of his and the crumbs lay near his belly.