I got this shampoo shortly after getting my hair done, from a hair salon. It's a little pricey at about £10 for a 250ml bottle, but so far so good, seem's pretty worth it :)
The shampoo is completely purple... I have no idea why it's called SILVER shampoo! It literally makes your hair and hands and everything purple! So you have to make sure you wash it off and wash your hands really well :)

The purpose of it is to eliminate yellowish tones from your hair. Blonde hair yellows really quickly because of sun and pollution, so if you hate that yellow-ed look, this is the shampoo which will help your hair stay a platinum / white shade :)

The hairdresser said to use it every time I wash my hair, but I don't feel the need to do that. I do it probably once a week at the moment, and haven't noticed any yellow tones so far :)
Definitely a great buy ;)