One person is very tall, but the other is very short. The big man is wearing a hat, a green jacket and yellow pants. The short man is wearing a blue hat, a white jacket and black pants.

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Is the passage above grammatical? Would you check it, please?

2 answers

It is grammatically correct, but why don't you designate the color of the tall person's hat?

"Big" is not quite the same as "tall." Tall refers to just the vertical dimension, while big can suggest being heavy (wide) too.

I hope this helps. Thanks for asking.
The only other thing I'd add is that you should include commas before the conjunctions in series:

...a hat, a green jacket, and yellow pants.

...a blue hat, a white jacket, and black pants.

http://grammar.ccc.commnet.edu/grammar/commas.htm
See #1.