My own hair color was once blonde, now a lot of gray exists.
There blond gave me the color Khadi no problems, I dyed any test strand and blonde equal to the whole head applied the new color.
The first time I leave for all 30 minutes, because the manufacturer can develop a red tint after half an hour, I wanted to avoid.
Result: on the gray proportion showed an unsightly green that had not disappeared even after a week.
Then I again stained 45 minutes residence time, back greenish, sigh ...
To dye before applying a test strand, as recommended by Khadi, would have been better in this case ...
The next attempt was with 2 parts Khadi blonde and 1 part pure Khadi Henna red and 30 minutes of exposure.
The color now looked good, but was for my taste a bit too red.
Then I again only blonde tries Khadi, but leave for 1 1/2 hours (this time with prior sample strands coloring).
Tadaa! This means my current favorite color found! A really nice Mittelblond without gray as desired!
And despite the many colorations in a short distance the hair are not attacked, vegetable dyes are simply much gentler than the usual chemistry!
Conclusion: Each hair reacts differently. Dyeing a test strand is advisable, so that one can create his favorite hair color without a few days to look strange. The exposure has on the tone with me really decisive influence. For sample strands I collect a while hair from my brush, is gathered up two small tufts, and then put them in a glass dish with a little attached rührter hair color. Then I can try two different exposure times and determine the result before dyeing. Worked out well!