Red: Almost invisible, this gaseous POKéMON cloaks the target and puts it to sleep without notice.Yellow: Said to appear in decrepit, deserted buildings. It has no real shape as it appears to be made of a gas.Gold: With its gas-like body, it can sneak into any place it desires. However, it can be blown away by wind.
Prof. Lotus' Notes: Ghastly is a portmanteau of Gas and Ghastly. Some Pokedex entries state that Gastly is born from poisonus gas, and Gastly with it's evolution line are the only Poison Ghost types as of Gen 7.