I have three balls.
1. One is white, another is green, and the other is yellow.
2. One ball is white, another ball is green, and the other ball is yellow.
3. One is white, another is green, and the third is yellow.
4. One is white, another is green, and the rest is yellow.
5. One is white, a second is green, and the third is yellow.
6. I have three balls; one is white, another is green, and the other is yellow.
7. I have three balls: one is white, another is green, and the other is yellow.
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I wrote down all possible sentences.
Q1: Which ones are not grammatical? Do you have some more available?
Q2: In Sentences 6 and 7, do we have to capitalize 'one' like 'One' after the semi-colon or colon?
4 is incorrect.
6 would be correct if that semicolon were a colon, as in 7.
The others are fine.
After the colon in 7, yes, you should have a capital O on "one" because you are following the colon with a complete sentence. If the words/phrases following a colon do not make a complete sentence, then you don't need the capital letter there.