In the early to mid 80's a cartoon movie about a robot it was three separate parts, one was red, blue and yellow they came together to form a single robot that fought evil robots, and other things it also had saw blades for weapons that came out of its hands. What was the name of that movie?

I think you are referring to Transformers. It was a big cartoon in the 80's and into the 90's. Optimus prime was the leader of the autobots (good guys) and megatron was the leader of athe decepticons( bad guys). If it isn't that I can only guess the power rangers but I believe that was later into the 90's.
I hope this helps :)

There was another 80's animated show called Voltron in which 5 different colored robots ( red, blue, yellow, green & black ) would come together to form a single large one.