1. I have three balls; one is blue, another is green, and the other is yellow.

2. I have three balls. One is blue, another is green, and the other is yellow.

3. I have three balls: one is blue, another is green, and the other is yellow.

4. I have three balls. One is blue, another green and the other yellow.

(Which expressions are right? Are all grammatical?)

All are correct, but #3 is the best one. The colon there is better than the semicolon in #1. #4 needs a comma after "green."