Look into a banana wrasse or sunset wrasse (same fish). As juvies, they are pure bright yellow with two small dots. As adults, they are nothing less than amazing. They can grow larger than what you are looking for though. They can max out at twelve inches but will take forever to get there. If you are in an area with local clubs, you can trade it later.
A mystery wrasse is full of color as a juvie through adult. They grow to a little over four inches.
And then there's ur wrasse which can grow to around six feet. But I'm sure you won't mind. (wrasse joke)