Where can i find silver hair colour [platinum]?

try the CVS or RITE AID

It depends on how dark your hair is. This color is achieved through a process called lifting and toning. You have to get your hair as light as you possibly can (minimal traces of yellow, if any at all) and then color over it.

First you must use bleach to lift your hair. You will need to mix the bleach in a 1:1 ratio with developer. The higher the developer number, the more lift. I suggest 20 volume to use only at your roots (it will not burn your scalp, and the heat of your scalp will make it process faster than the rest of your hair). For the rest of your hair, use 30-40 volume. Again, the lighter your hair is, the less lift you need. Consider the health of your hair when you choose a developer.

After you have lifted your roots with 20 volume, (you may need to do this several times) move on to the "mid section" of your hair with your 30 or 40 volume. Finally, do your ends. After you have lifted almost all traces of yellow or "brassiness" from your hair, It is best to use a "toner". You can find this at Sally's or any beauty supply store, just ask a clerk to help you. In looking for this toner, the label should read something along the lines of 10B or light ash blonde. I suggest asking the clerk to help you with this as well. Just tell him/ her you want PLATINUM. Follow the mixing directions, and KEEP AN EYE on this process. Your hair shaft is very porous (open) right now from bleaching. You may not want to leave it on as long as the directions suggest. FYI: It's okay if your hair is a little blue, purple, or grey initially- this WILL fade as you shampoo.

Depending on how much you had to lift, your hair is going to be damaged. Buy yourself a DEEP conditioner and use it like crazy. Get a hair cut, or a trim, whatever, you're going to need it. Avoid heat implements for a few days if you can. Good luck!

You can find a hair spray type deal at a halloween costume store, they have all sorts of colors.