Red is the truth (GM Neo's information is absolute, known innocent also reach this level, as well as myself)
Blue is for theories (or ideas for courses of action) although you could nerf the definition to follow others info which isn't quite red, but sounds nice anyway. The only time I let my guard down with it was with Ellipsis.
Purple is as good as red, but culprits can lie while using it...kihihihi... (it means, unsure if lying or truth)
Grey is untrustworthy stuff, notice it was placed for people we knew were guilty.
Variations of purple are what tilt to grey or blue, or red, etc.
Gold is to say magic did it fuck your shit and speak the future.