What happens if I use thunder wave on Kecleon. Then he OHKOs me and I send out Graveler. Graveler used Magnitude 5. is Kecleon still Paralyzed?
I never splashed so hard before
Yes, Kecleon will be paralyzed but his type will change to Ground. Keep in mind that when you use Thunder Wave, Kecleon's type will not change as Color Change only takes affect when hit by a damage dealing move.
Source: Experience and the page about Colour Change on here