What would make my premix change coulor?

[zx|muppet]

Had some Mayhems pastel red and it's turned purple. Drained the system and there doesn't seem to be anything in the system that I can see. I what else might cause it?

 

[gcaster]

Residual dye in the loop?

Highly doubt that it'd be copper dissolving but when in solution copper is blue.

 

[zx|muppet]

Replaced the rads, tubing and cleaned all the barbs. Also took the gfx and cpu blocks apart and cleaned that out. So meh dunno.got a di water loop running at the moment to check its clean. Anything else i can put in the loop to check everything is clean before i start running it with pastel again?

 

[PhillyDee]

Deionised or white.