this is getting frustrating

i have naturally black hair and i have some white hairs. i have been dying my hair dark brown for a couple of months now. i leave it in for 40-45 minutes because of the white hairs and recently, i tried dying it to medium brown. i thought everything would be fine, but to my surprise i got uneven results. the roots were medium brown, the rest was still dark brown. do i have no hope in ever switching to a different color dye? must i always have to strip my haircolor to get even results? i dont know if i am doing something wrong. will someone please help me? i think its time i need to know what i do before i do it. thanks alot.

will colorfix affect my virgin roots, resulting in lighter roots than my all over color? also, since my previous dye job made my roots medium brown, will this result lighter than the stripped dark brown color?because i dont want to have another disaster. thank you so much

Dont quote me on this,but I used the swarzkopf phantom that works with sulfur like colorfix,and it didnt change my virgin hair at all.I only hads to strip the top half,but put it on my whole head,and it didnt remove any of my hairs natural pigment that hadnt been dyed.Plus colorfix is supposed to soften new growth to take dye better.And yes you can dye your hair lighter.But like bryan said,dye cant lift dye.Your hair stayed dark because the colors were overlapped.From now on I reccomend only doing the roots.And if you dont like the color,strip it out first then dye.But be careful even staying dark can take its toll.Your hair can become damaged to a point where your hair will look patchy when dyed.This can be remedied too,but for someone who's been there I dont recommend it.Good luck.