I got these flip flops that were completely white, to white for me, and I decided to ad a little bit of colour to them. I am gonna share itwith you so you could do it yourselves.
It's easy and don't cost you.

Take a fabric you like, any colour you like. Cut it into 4 strips 3 cm wide, 30 cm long. And also 2 strips wide enough to wrap around toe piece.
Take one strip and hot glued it where straps and toe piece meet. Now start wrapping fabric around the strap , I've glued underneath the strap just in case. Wrap all around the strap til the end. Put some glue and tuck ends of fabric in a hole where the strap ends. Do the same thing for the remaining straps. Same thing for the toe piece, put some glue and wrap it around.
As you see, I've aded bows, made of tiny black rope. It needed something to lift it up.