When posting a problem on a discussion board and then solving it before someone else replies, it's good practice to leave the original post and edit the solution into the top or bottom of it, for posterity. Some day someone will search "ffxiv chocobo not changing color" and this post will appear as a result, but they won't know if your solution applies to them or not.


In re: feeding all the fruit, it's also worth noting that the chocobo's color won't change until giving a fruit results in a message about the chocobo's plumage. This message indicates that a new color has been set. At this point, the chocobo needs to remain stabled for the aforementioned time as per Frizze's post or the change will be undone.