Can I play a different colored Draw 2 Card on top of a Draw 2 Card in Uno or Uno Flip
Yes, Player C can play a different colored Draw 2 Card on top of Player A's Draw 2 Card.  


  Draw 2 Card - ... This card may only be played on a matching color or
  on another Draw 2 card.


Here's a great place to read the rules yourself:
From mattel.com: https://service.mattel.com/instruction_sheets/42001pr.pdf