What's in?

おしゃれ講師Christinaがこの夏の流行色について
教えてくれました♪

So what's in fashion for this season?
Well, the metallic blue nail polish seems to be
the height of fashion. Actually, all types of
blue nail polish colors are popular at the
moment. Not only that, but acqua green
nail polish is following behind blue as the
popular choice for this season. Recently, I
bought two different blue nail polish colors to
try them out. I'm hoping for some sunny
weather to come soon so that I can paint
my toe nails with the metallic blue nail polish.
I'm imagining my toes are going to look
rather ravishing once they're painted with
such a vibrant blue color.

what's in fashion?="in"は流行のと言う意味があるので
この場合は、「今の流行は何？」という意味合いになります。
height of=〜の極み、まっただ中
height of fashion=the most popular fashion now
ravishing=とても美しい、魅惑的な=charming
vibrant=明るく強烈な、鮮やかな
=Bright, colorful,lively-energetic