No action should be taken.
Flip Card is played, the UNO FLIP rules only state that the Discard Pile is to be flipped. Not that there should be any action taken regarding to the new face up card.
Flip Card – when you play this card, everything flips from the Light Side to the Dark Side.
Once the Flip card has been played, flip over the Discard Pile (the card just played will now be on the bottom), then the Draw Pile, then everyone’s hands must flip to the other side.
This new side will remain in play until another Flip card is played, changing it again.
This card may only be played on a matching color or on another Flip card.
The card turned face up (after a flip) will always be another
Flip Card. Except for the first "flip" of the game (which will produce the back of the first card turned up at the beginning of play) or if the Discard Pile is being shuffled due to lack of cards in the Draw Pile.
If a "flip" produces a
Wild Draw 2 Card or
Wild Draw Color Card, then the rules are not clear as to who gets to choose the color.
My interpretation is that the next person (aka the person to the left) gets to choose the color.
Wild Card – ... If a Wild card is turned up at the beginning of play, the person to the left of the dealer chooses the color that continues play.
But another interpretation would be that the person playing the
Flip Card gets to choose the color.
UNO FLIP Rules