BLUE BIRD hair

[Luja.]

hey everyone

I am watching BLUE BIRD PV right now

Well, I just thought about her hair in there - she filmed the PV when she still had brown long hair, right? Her hair looks brighter and shorter in the PV. I am asking because she sings the song on her AT06 and the PV is playing in the background while she's performing - still with brown long (m)u hair.
Was this a wig or extentions? Did she change her hair just for the PV?
Or am I in the wrong time line?

Thanks in advance!