BLEACH&COLOR HAIR? Questions?

I am about to be 21 and want to do something fun with my hair like bleach sections of my hair then dye it a dark purple ..goin to sallys soo my question is... do I bleach my hair with a cap then wash bleach off with cap still on then put the color in? Or would I take the whole cap off and look for the bleached hair..i want small purple streaks around my head.. My hair is dark brown thick and wavy/curly. Also what to use after to keep hair real healthy