I was reading an explanation online regarding the difference between いつも, いつでも and いつまでも. At the bottom of the article there was this sentence, which seems to be taken from a banner ad:
いつまでも美しくいるために
And here the translation taken from the article:
(in order) to be beautiful forever
I understand the meaning of いつまでも here, but I can't figure out the meaning of 美しくいる. I would translate it as "be in a beautiful way", which doesn't make much sense. Is there another meaning or it is just impossible to translate it literally?