Sure. But I asked you which application you were pasting the text into. I don't see the name of any application in your response. The answer depends greatly on which application you are using. Every application is different. If you tell us the name of the application, I might have the same application on my computer and I can tell you how to create a macro to change the first line to red. Did you mean red highlighting or red text?
Is the app you are using to edit your documents Pages? Or Microsoft Word? Or Notes? Or TextEdit? Or something else?