How Do I Change CSP Backgrounds?

[SSBM_Mirage]

I'm in need of help. I've been creating some retextures for my melee characters but I have no idea how to change the character selection screen's portrait background. By this I mean when you press L or R and the backgrond portrait changes color ie. White Marth pressing L changes to a white background with a blue line to match the character. How does one change this to a different color?

 

[Achilles1515]

http://smashboards.com/threads/the-complete-csp-compendium.380315/page-9#post-21199961