T5nitro,
Thank you for your questions on the Powder Brown Tang. This fish goes through a coloration change as it matures from Juvenile to Adult. Generally, the Juveniles are more colorful than Adults, but there is not a specific size at which they are the most or least colorful. Other factors, including health and aging, may reduce coloration of the Tang. We hope this information helps answer your inquiry.
Nate M.
LiveAquaria
Drs. Foster & Smith