I love your blocks. This will be a pretty quilt.
As for me, I would use a small black border strip, maybe 2" finished or 3" to stop the action in the center. Then maybe the same size in the background fabric. Then maybe a 6 to 8 inch finished of one of the reds for the outside border.
Like someone said up above.... Lay your first border fabric lengthwise down the side. Leave the size you want showing, then lay the next color of top of it. Then lay your final border fabric. Take pictures of what you have designed. I don't know why but seeing it in the smaller version really helps see if it is going to work. Make any adjustments until you like it. Then, start cutting your border pieces.
You layout is 5x5 which equals 60x60 inches finished as it is. Measurements when adding the borders would be
60" Wide with just blocks
6" - for the 2(each edge) x 3 inch borders
6" - for the next 2 x 3 inch borders
12 - for the last 2 x 6 inch borders
84" will be your finished quilt and it will be a square.
That's a fairly big quilt. This page gives you some ideas what sizes are normally made.
https://suzyquilts.com/quilt-sizes-chart/ There is nothing that says yours has to be any of these sizes. Quilting is one of those things where you get to make the choices.
If you want, sew your blocks together, then start laying out your borders and show us pictures. We are more than happy to give our opinion, but it is "your" quilt. You have the final choice. There is no right or wrong.
Edited to add. You might want to start with maybe a 2" background border to float all your blocks, then go to a different color, either black or red, or whatever you want to try. I've made quilts with 4 borders and loved them. And some with only 2 and they were fine. Have fun!!!!