Ok, so I'm not grey ... yet

And I am sick of paying to have my hair colour, when after all, it's not really nessesary.

SO

What is the best way to go about growing out your natural hair-colour??

I'm a dark brunette, the colour in my hair has a speck of red in it, so if I let my hair loose, I get this dark roots, with the "faded" red locks ... not looking good atm.

Would semi-permenant dye work?? I know it's not something that is going to happen in a week's time, but I really, really want my natural colour back