Inserting customized content at top of category sections

I want to insert customized content near the top of the blog home page depending on which category page someone is looking at…

for example lets say I have a category section entitled “red coats” and a different one called “blue coats”

When someone clicks on the “red coats” category section of course it will display all blog posts in a list on the homepage that have this category tag…

so right above the first post in this listing I want to be able to insert a custom piece of text content, for example:

“This is the red coats category where you can find information and products that are red in color.”

and then at the top of the “blue coats” section I want to insert some text relating to blue coats..

QUESTION:

What kind of code do I need to add for this and which file(s) do I need to modify in order to do this?

And then where do I insert my custom text content ?

Thanks in advance for any help!