Best shampoo to maintain coloured fair hair?

[Chicinwellies]

I'm about to fork out for my miracle worker hairdresser to colour my hair (full head foils and toner). It's been a while since I've given a monkeys about what I actually wash my hair with so wondered what shampoo and conditioner are best for not stripping away the colour....?

I always used the redken blonde glam range

Also a redken fan, wella sp is a good range for coloured hair too. Id buy from hair hq or look fantastic websites