Everyone is lying, because yellow coris wrasse isn't a coris wrasse at all (ya feelin' me
@Slocke ?). To my knowledge, banana wrasse refers to
Thalassoma lutescens aka yellow-brown wrasse, which gets to about a foot long, and initial phase is yellow with some red vertical striping (I think in the dorsal fins).
Yellow "coris" wrasse is a common name for
Halichoeres chrysus, which I call the yellow pig wrasse [Etymology: Halichoeres: Greek, als, alis = salt + Greek, choiros = pig, from fishbase.se], i.e. "salt pig". H. chrysus initial phase is yellow all the way through with cute black spots on the dorsal fins.
I think you have a yellow pig wrasse, but I'm not a wrasse expert... yet.