Uno Flip - What color do you play when a person flips?
https://service.mattel.com/instruction_sheets/GDR44-English.pdf


  Whether playing the Light Side or the Dark Side, on your turn, you must match a card from your hand to the card on the top of the DISCARD pile, either by number, color or symbol (symbols represent Action Cards; see FUNCTIONS OF ACTION CARDS).


The teal 5 is on top of the DISCARD pile, therefore the next play should be on the teal 5.