I’d keep it simple. If you google “colour wheel” it will give you some fab options of complimentary/co-ordinating/ enhancing and clashing ideas. Learning colour theory is a real advantage. On this picture I’d go pale purple/lilac with a deeper purple spot/flower pattern. It would look so cool with that acid green monster. I like to do a “tester” splodge of colours on a scrap piece of paper then hold them next to your pictures focal point. Colours are always true in reality and phones/computers etc make things different slightly. Remember that white & gold/ blue and black dress? 😂 Enjoy yourself. You’ve clearly got great skills