The L`Oreal Platinum is a great product, and providing it is applied and developed correctly you should have no problem.
As with all colouring you need to ensure you use the best conditioning treatments you can afford to ensure your colour and tone stay vibrant, as well as your hair been in tip top condition. ...More >
Always, always ensure you have a strand test done prior to a colour application especially when going to a new hairdresser.
Depending what DEPTH of brown your hair is you should be able to get a good clean blonde tone with tint, this is much kinder to your hair than any bleach.
Ask your stylist to take a strand test and apply a high lift tint with 12% peroxide. This should be left to develop for 30-40 minutes and your will see the result as well as the condition of the hair section prior to an overall colour application.