The bottle is light green and it says the name of the product in dark neon blue, and has a picture of Plankton on it. It has conditioner, as Plankton points out.
Role in episode
Plankton uses the shampoo to control Mermaid Man and Barnacle Boy. He visits them at Shady Shoals Rest Home, pretending to be selling dandruff shampoo. After applying the shampoo, he reveals the shampoo's real use, and he brings Mermaid Man and Barnacle Boy to the Krusty Krab to ruin its business.
When Plankton uses this product on Mermaid Man and Barnacle Boy, he falsely lists the name as "Professor Plankton's Dandruff Control Shampoo."