Love your goal, but that only works when one allows a timeline that is defined in years...
Consider taking a long read into the foundation of a great diet for an Amazon. Within the Sticky Thread: I Love Amazons - ... is a segment that defines that foundation; its base and building-up from there.
As you already know, the base is built around veggies and in addition, the available veggies in their 'home ranges' changes during the year as different veggies become available. What that means is that during a year, difference sizes, colors and favors become available and, that includes textures. What that means is that what may peak your Amazons interest maybe as simply as changing the way it is provided. After all, the same veggies change when they are fully cooked, par-cooked or served fresh. Then consider whether sliced, diced, etc, etc, etc...
Shock, there is no favor difference between different color pellets. But, there are very huge differences between different Pellet Manufactures. Some are of little value, some over-loaded with tons too much of important Vitamins, minerals, etc, which can result in providing to much of a good thing. Plus there are manufactures that use 'sugar' to get your Parrot to eat they're pellets. Sugar loaded Pellets can be a nightmare during hormonal season. Another background element and tool used by some manufacturers is the over use of salt. Select a high-end pellet and switch your Parrot over to it by using a Human Grade food coloring and slowly reduce the amount of color added.
The 'not' by accident food bowl: Amazons maybe choosy, but that does not mean that they can be easy to fool by simply providing different foods in different sizes and will wet mix, it is surprising what you can get them to eat by having something new near the same color and size of something that they have been eating.
One can put together extensive lists of different segments of their foundation diet.
Long story really short, if it is on your plate, your Amazon will have a much higher interest whatever you are eating.
FYI: What is included in your version of the term: SEED?