DI Resin color question

[Klyph]

I ordered a small bag of color changing DI resin. When I get it, there was a small hole in the bag. I wasn’t worried that it came that way, but I just opened it today, and the grains had both blue and brown in it. See pic. Should it have done brown specks in it, or should it be completely blue?

 

[KC's CNC Creations]

it's a mixed bed, perfectly normal color.

 

[CapeCoralDan]

Normal color, will turn orange went spent

 

[RedReefer]

Normal color. Mixed DI. Use it.

 

[Garf]

I’m interested in how they make it color changing. Is it something like a food coloring in the regeneration process which gets replaced by other elements during depletion? Or perhaps a pH indicating dye in the anion regeneration, like bromophenol blue, which changes color as the Anion depletes and the pH decreases. Anyone got any ideas? I’ve regenerated my own resins for over 15 years, but never used color change resins.