Did anyone ask Rapunzel how she get her hair back to blonde?

You mean, to the little girls who think she is real? My 5 year old niece thinks she's real. It's funny when I showed her the video of Rapunzel getting coronated and she pointed out "She looks different". Maybe because she remembers this Rapunzel that's in your photo, I'm not sure. My oldest niece told her that she just looks different from the movie, that people look different in real life. XD

But my niece never asked me how Rapunzel got her long blonde hair back so I never thought about it. I don't know what the Disneyland Rapunzel says to explain it. I can't think of an explanation.

Well, they probably just decided to have the Disneyland Rapunzel with blonde long hair, because thats what the character started out with in the story in the movie and is most popular for.

i really don't know but it's just better for the little kids because they really only remember her with blonde hair

Maybe they did it just so it wouldn't be a movie spoiler. I also think that they just thought that since she was that way the whole movie they would leave her like that.

Um I found this info in Disney Wikia. I'm not sure if it's true but anyway.

The official explanation for her Park appearance is remnants of the magic within her after healing Flynn gradually allowed her to grow some hair back.

I don't think it matters to be honest. Rapunzel has blonde hair in the disney princess francise and on the disney princess website.