What is the best dye to use to rid grey hair?

I tried many but they don't last long. Who knows the best product to use?What is the best dye to use to rid grey hair?
I was having a look around and found this testament!!!





';I have tried almost all the ';box'; hair dyes and found that loreal preference works best....not the cream one, that does not cover gray. My hairdresser told me to go to Sally's and buy the processor and color separate and mix two colors. My hair is auburn....medium to light....so red dye does not stick to gray hair...mine would wash out in two weeks....so I mix one full tube of light golden brown (loreal excellence for 100%gray coverage in blue box at sallys) and mix it with a half tube of red or auburn. My hair is long so I need one and a half for coverage. If your hair is short or medium length mix the tubes half and half....its one tube with 2.5 oz's of developer...or I use one and a half tubes with 3.75 oz's of developer....I leave it on for the full 40 mins. also that makes a difference with gray coverage. I dye my roots to about 4 inches out and leave on for 20 mins then pull the rest of the color to the ends for the last 20 mins.....I am 42 and have to cover my stubborn grays every 5 weeks...sallys is the way to go....good luck my silver strand friends.... ';