Coloring in between lines?

Hello figma community,

So I just got into figma 2 days ago, and I was trying a design that came to my mind but I got stuck at the very first thing.

I have Drawn these lines with the pencil and grouped each 2 parallel together. But I cannot find a way to colour in between. Is it even possible or do I have to use a rectangle, rotate it, and have its borders go out of the frame ?

Thank you for reading :slight_smile: