Same way as dirty blond hair. Bleach it! Make sure you take it to a light yellow, don't be scared, there's a banana yellow and shortly after it'll turn light yellow. Now. White hair... you cannot bleach your hair white, keratin has a light yellow color so if it's 'bleached' white, that means you've destroyed all the keratin and it'll very shortly feel like gum. In order to get it white you have to bleach it to pale yellow and then use a toner to get it the rest of the way. Violet tends to be the best as blue sometimes catches and turns gray. Look up the 'Levels chart'.
Some people get lucky as most bleach usually has toner mixed in, like Prismalight bleach has violet, blue, and gold packets, and sometimes the toner in the bleach alone is enough to make their hair white. I always preferred the blue bleach. If your not one of those lucky ones like I'm not lucky, go to Sally's and pick up a platinum toner, the protein filler platinum toner mixed with Manic Panic's virgin snow I find works for me. Either that or try getting your hands on some Redken Shades EQ. That should give you white.
As for pastel pink... you'll prob. have to find someone who can go into a beauty supply house to get it, but Pravana makes two pinks. A magenta and a pink rose. The pink rose one is a gorgeous pastel pink that goes on heavy and then progresses to a lighter and prettier pastel the more you allow it to fade. Eventually it will fade completely back to blond. Which I loved because I could do another funky color without bleaching it again.