I never understood it either, but I think it may have come from when ISU had the Cy with the Tornado body logo. The tornado was outlined with a blue line. It seems like that was discussed here before. Looks like that may be the logo on the shorts in the photo?
Did we ever wear navy blue uniforms? I swear we did this for a game or two sometime under Floyd but I've never been able to find a pic of it and I might just be going crazy hear.