Let's write!

Choose a character and imagine that they are describing a person, object, or scene to someone - say, they're on the phone and trying to describe what they're looking at. Write what they say, paying close attention to writing their dialogue in their voice. Don't write anything else - no description, nothing that the other person says. Just the chosen character's few sentences of dialogue.

Now, choose another character (doesn't have to be the same work or fandom) and do it again, writing their description of the same person/object/scene, in their voice. Observe how different the dialogue comes out, between the two characters.