Since it's quite dark inside a freezer, I expect the color of the glass is of no consequence.You can store nic in your freezer in dark amber glass bottles for alot longer than a year.
I think the answer to the "right" nic for long-term storage is simple: Get the cleanest nic available.Choosing the right nic for me after all this time is another matter entirely so I feel like a newbie in that regard.