Questions on managing toning

[ikaros]

I'm agnostic on toned coins. I don't go looking for them, but neither do I avoid them, so seeing that a few of my Statehood quarters in a Littleton folder are starting to change colors is neither a crisis nor cause for celebration.

 

One is going a nice sort of gunmetal blue; the others are going orangeish.

 

Is there a way, without artificially treating the coins, to encourage the process and maybe even redirect it a little, like changing the way it's stored? Are there storage options that will generally produce a nice, even sheen of color rather than blotches?