Can I p a hair follicle test by dyeing my hair?

I've stopped smoking weed 4 day ago. And I used to take a hyrdocodone everyday, but stopped taking that 2 days ago. If I dye my hair, can I p a hair follicle? Also I've heard that a hair follicle test is only 50% positive, is this true? I've heard that a hair follicle only tests to see if you were clean and got dirty, or if you were dirty and got clean... True? Thanks!