Yesterday, I saw a man . . . . . . . . green hair.

The correct answer is D: with.
Let's break down why:

Prepositions are words that show the relationship between a noun or pronoun and other words in the sentence.

In this case, we want to describe the man's hair.

* "to" (Option A) usually indicates direction or purpose. It doesn't fit here.
* "of" (Option B) indicates possession or belonging, but using "of" here would sound awkward and grammatically incorrect.
* "on" (Option C) is typically used for surfaces or locations.
* "with" (Option D) is used to describe a characteristic or feature that someone or something possesses. "A man with green hair" means a man who has green hair. This is the most natural and grammatically correct way to describe the man.

Therefore, the complete and correct sentence is: Yesterday, I saw a man with green hair.