As stated above, sunburst and blotched anthias are just fine kept singly. As do pink square and bimaculatus anthias, but 55g is on the small side for these 2.
Female pencil and flasher wrasses are pink, as are a few fairy wrasse females. Halichoeres trispilus stays pink through it's life. Aurora goby has pink stripes. A talbot damsel is a peaceful damsel that is predominantly pink.
Avoid sixlines and mystery wrasses, as well as purple/magenta dottybacks(though not orchid dottybacks) unless you are prepared for fish whose aggression increases over time.