As a first approximation, there are no stable colloids. I suggest you look for kinetically stable (i.e. metastable) colloids. The academic community is divided between those who insist that no colloid system is stable and those who offer theoretical reasons why certain systems are thermodynamically stable. I used to believe no colloids are stable (thermodynamically) but changed my mind (based on the scientific literature at the time). Unfortunately, that was decades ago, and I'm not able to give you chapter and verse rationale why certain colloids may be stable. To be "stable" the particle needs to both not fall (match density to its media so that thermal motions (and mechanical vibrations, possibly) overwhelm any tendency to fall) and more difficultly have a lower free energy in the highly dispersed state, specifically it must be electrostatically repulsive towards other particles and have virtually no tendency towards Ostwald Ripening. This limits your options to organic (charged) polymers and if you can "structure" the water, that's all to the better. If I recall certain acrylates were able to be synthesized into particles fitting those requirements, but it was a long time ago. Permanent is a long time, I really doubt you need permanent. I'd bet 50, 100, or maybe 200 years would do just fine.