You can feed your chocobo all in one go, however you’re not just going to feed them apples.

https://ffxivchocobo.com/en/desert-yellow/dalamud-red

Here’s the calculator for dalamud red, follow that to a T, get extra fruit just in case. What you’re going to do is feed fruit *one at a time*. When you get the message that your chocobo is changing colors, switch to the next fruit on the calculator list. Keep going, IN THE ORDER the calculator states.