I have always thought the Plumeria flower looked a bit like natures pinwheel so quilting the petals will be done to express that spinning type movement. I have at first chosen 3 HOT threads in pink, orange and yellow. It's wonderful to have a large thread stash.
Starting with hot pink.
Moving next to HOT orange. I try to 'lock this thread into the previous thread where possible. It makes a easier viewer transition from one thread to another. My old watercolor teacher used to call this technique "KEYING" .. ie locking one thing into another for cohesiveness of design.