The white and blue caddies were sometimes mixed up in the waning years of the format. RCA kept releasing new titles for a few years after they ceased production on the players, so it's possible they were simply using what caddies were left in stock regardless of the film label they glued on.

I've seen discs with blue outer shells and white inner sleeves and vice versa.

All mono CED releases of stereo films are clearly marked as such on the back label. "Mono sound for videodisc." Early players and titles were all mono, one thing that gave Laserdisc an early advantage.

The OT CED releases were all stereo.