Okay kiddo, so imagine you have a really cool drawing that you made with a regular pencil but you want to make a few changes. Maybe you don't like the way the head of the person looks, or maybe you want to add a tree in the background. A blue pencil is kind of like a special pencil that grown-ups use to make changes or edits to things like books or papers.
But why is it blue, you might ask? Good question! The blue color makes it pretty easy to see and tell apart from the regular, normal pencil writing. When someone uses a blue pencil to make changes, it's called "editing" and it means they are making different marks or notes on the paper to make it better or clearer.
So if you have a drawing that you want to change or make better, you could find a blue pencil and use it to make changes just like a grown-up editor does with books and papers. It's just one way to make something better and more polished!