Blue
Young
The blue radical and the blue kanji are exactly the same.
Additionally, this can also mean young. You can remember this because young people have potential as limitless as the blue sky!
せい, しょう
あお
None
You've been feeling really blue. Mostly because your skin, hair, and eyes have all turned blue. It was an out-of-the-blue transformation! But now someone places his hand on your shoulder and points at your saber (せい). It's blue too! You aren't alone!