Chocobo Colouring woes

[Kaelah]

Check out this thread:
Microfeeding.

This calculator will help you work out how much of each fruit to use to get the colour you want:
Calculator.

For the colour to change, you need to see a message that says something like "[Name] is beginning to grow new feathers!" That tells you that you have reached another colour. The new plumage message is just a generic auto response to feeding. Means nothing.
You don't need Botanist to grow the fruit. You can buy the seeds with allied seals, which you get from hunts. Cost 15 seals for 1 seed. Then you just need a FC house to plant them. They do take a while to grow if you don't have fertilizer. You generally get around 27 fruit from one seed. (Or I have anyway.) I think it depends on what soil you use and fertilizer though.

Hope that helps.