Rainbow Blaxx 레인보우 블랙 Was A Sub-Unit Derived From The South Korean Idol Group Rainbow. The Members Chosen For The Group Are Jaekyung Woori Seungah And Hyunyoung. Their Début Mini-Album Was RB BLAXX 20 Jan 2014 . The Lead Single For RB BLAXX Was "Cha Cha" And It's Music Video Was Released The Day Before The Mini-Album.