Six Colored Balls Puzzle

The Puzzle:

Six Colored Balls
We have two red, two green and two yellow balls.

For each color, one ball is heavy and the other is light.

All heavy balls weigh the same. All light balls weigh the same.

How many weighings on a beam balance are necessary to identify the three heavy balls?

(A Martin Gardner puzzle)
Do you have the answer? Check against our solution!