Bleaching your hair ...

Im about 14 years old and my parents dont really like the idea of me having a dif. hair color then my normal.. but then they KIND OF allowed me, I wa plannin in bleachin the back part of my hair ( in the back like when you tie your hair in a pony you see...

th elower part different colored) and I know depending how long you put the bleach will affect your hair colors lightness... but im using a semi-permenant hair dye. And im not sure if ill be allowed to dye all the time. so my father will kinda go mad if it shows a lot or anything abnormal looking!
I have dark brown hair, but I really really really care about my hair like I dont want it to gray AT ALL and other bad side affects that can happen! and I know once the semi dye ( cant dye for real) will wash aaway someday and leave me w/ teh bleach color and as your hair grows out the color of bleach will fade from teh ends and start going up and up andup until it MAY reach your roots from the back or whatever.. soo I lost my point but I NEED HELP! do you guys know what I can do? like can it grey my hair, and do you know good dark colors for my hair, and teh colors that the bleach can do if you leave it on for a specific time and some tips thanks a lot

easy answer just don't dye it because believe me you won't be ab;e to stop bucuz her hair gets really ugly when it starts to grow out just leave it and get some bleach hair extensions