I've been asked the question about home haircolor, so here is my answer. Don't do it! I don't say this because I'm afraid I will be out of job; that will never happen because someone will always botch up a home haircolor job and I will be there to fix it. I do make a lot of money off home haircolor corrections so maybe I should say do it so I can charge you lots of money to fix it! I kid, I kid. My reasons for not liking box color are many. First and foremost, the stuff they put in there is junk. For example, metallic salts: they work by coating the outer surface and take away the shine from the hair. Many companies get around this by adding other chemicals with light reflective properties. If you decided to go to a professional for say, highlights, some of chemicals in the box colors can react badly with the professional colors (i.e. hair falling off) so buyer beware there. Next, you get what you get color wise with a box color. There is no custom formulation like you get in a salon. Rarely do I ever put just one color on someones head. I usually mix 2 to 3 colors to get my custom color. Finally, the developer is usually only 10 or 20 volume which might be OK for going really close the natural color but not if you are hoping to go a couple of shades lighter. It will usually come out very warm or even orange. If you must do some sort of touch up in between I'm cool with the root touch up kits like this one from Nice & Easy
Just touch up the front of hair and your part. You should be able to get a couple more weeks out of your color job.
try a glaze like this from Frederic Fekkai (sephora or macy's carry it)
or a hair powder spray like this one from Bumble & Bumble (bumbleandbumble.com)
If you have dark brown or black hair you can always use mascara to cover up those greys in between color it's another form of temporary haircolor.