Best unnatural hair dye? Manic Panic, SFX, La Riche...?

I'm going to dye some light blonde, real hair extensions light violet, and I want to know what is the best hair dye?

I won't be washing the extensions (they'll be worn only on the weekends, so it's not like they need to be), so should I still be concerned with fading?

Also, La Riche is the only one available to buy in stores (in my city).

HELP?

Best unnatural hair dye? Manic Panic, SFX, La Riche...?

I've used Manic Panic and it really does work great. I haven't used SFX but I have heard AMAZING things about it. Never heard of La Riche.