My hair grows very fast, ¼ a week. (Yeah for vitamins!)

 I usually need to recolor my medium brown hair every three weeks, because all my crown hair is 100 % grey/white, and very visible. ( I see roots at one week post color)

I do use a color deposit treatment in the shower once a week, which keeps the color super bright and nice, but of course does not tint the roots.

I would like a root touch up before Thanksgiving, but since I just colored last week, its still a bit to soon to recolor full head, even when I do roots only, then pull through.

Can I mix the ION color with some developer and do visable roots only?  (like you do with the drugstore root touch up kits) I have both 20 and 30 developer. (I use 30 on normal color, since I do red) Would 20 be okay for this?

Since I will not need a full tube of the color, is it possible to reseal the unused colorant (unmixed) and reuse it again at a later date? Or will I be wasting a full tube once I open it?

The Root Color Kits allow you to only leave color on roots for 5 to 10 min, instead of full development time – would that be possible in a case like this also, since I am only doing about ½ inch of regrowth, that is white grey, though not resistive?