Yellow!!!!
I have a Midnight Blue P5 as well. I am doing my calipers, my strut bar, and my CAI in Mazda Vivid Yellow.
I am ordering a CAI from BigBen when I get the funds, the strut bar will be done by my friend's day who owns a body shop. He will sandblast the red off and then throw on a couple of coats of yellow then a clear enamel to save the color.