Just wanted to share my experience - I have been coloring my hair at home for quite some time too; the top and sides (near the temple) are more white than my natural dark color. I had always used box colors from the stores (i.e. Target, Walgreens, etc.), however, I found a thread on this site regarding salon quality color (i.e. Wella Color Charm, etc) you can buy from Sally Beauty. Some of the comments included the color being richer, the dyes were better for your hair, gray coverage was better and it was economical. Folks also mentioned adding this product called Gray Magic to your color which would help your color grab the grays better. (How we can buy salon quality products without a license is beyond me though?)
Fortunately, I found a Sally store in our area. I purchased the color ($3.69?/box), a large bottle of developer ($5.30?/bottle), a box of gloves, gray magic ($.99/single application), an applicator bottle. Although the initial investment is about $20, it really is economical considering the developer can be used several times which would mean only purchasing the color in the future.
So far, I've colored my hair 3 times. I do not find that the gray coverage lasts any longer than store bought colors, even with adding the Gray Magic. Like the previous post mentions, it's likely because the gray grows out and not so much that the color faded. I do find the texture of my hair after coloring is not so dry (like straw), the color looks richer and does not fade as quickly. So while I was hoping to color my hair every 6 weeks like they recommend, I still need to do it every 3 weeks (and that's with my grays showing considerably because my natural color is dark).
The other tip I learned on this site is that adding apple cider vinegar to the shampoo and conditioner, will help your color to keep from fading so quickly. I've tried this with my conditioner only and did find my color did not get brassy or as faded. I'm still looking for a better shampoo & conditioner for colored hair - I'm one of those with coarse hair and need a heavy conditioner. Any suggestions?
Hopefully, there be more posts with more valuable tips! I'm learning so much from this hairstylezz.com/best-dark-and-light-brown-hair-highlights-styles/ site!