Yeah, I could have sworn that I read somewhere about Amanda saying she wouldn't wear a blonde wig for when she plays Sam after Stargate: Atlantis' last episode. I don't know how hair colour dying works tbh but I was always under the impression that her blonde hair in SGU was actually her blonde hair. Is it possible to apply hair colouring on top of hair colouring? If so then maybe Amanda applied blonde hair colour dye over her dark hair colour dye for SGU?