Real World article
(written from a Production point of view)

Richard Snell Designs, Inc. was a makeup design company headed by the late Richard Snell. This group of makeup artists did creature designs for Star Trek IV: The Voyage Home and also designed the Klingon and Vulcan makeup for Star Trek V: The Final Frontier and Star Trek VI: The Undiscovered Country. The company also worked on Star Trek: The Next Generation.