What you are referring to is brassiness, when blonde hair starts looking more orange.
The safest way to get rid of that is to wash your hair with a blue or purple toned shampoo. There are many out there in the stores, I believe John Frieda makes one called Color Renew for blondes. There is also L'Oreal Brass Banisher.
Polytar shampoo is for people who suffer from psoriasis, it is expensive and it's not good for you to use excessively due to all the chemicals. It is not meant for removing brassiness from blonde hair.