Violet Jellybeak
Yellow triangle - √
Green heart - √ 
Red crescent - √

Rainbow Jellybeak
Yellow loop - √
Rainbow heart - 2 violets beaks
Blue triangle - √

CANDIES
Candydevil - Berries - Round
Lollipup - Fruits - Loop
Cherrymole - Berries - Triangle
Sweettooth - Veggies - Square
Sugarsnout - Fruits - Pentagon
Jellybeak - Birdmix - Heart
Chocobugs - Veggies - Crescent

  If it's a Round, Square, Crescent:   
  small left leaning bud ----- red, green or violet
  small right leaning bud ----orange or blue
  fat bud  --------------------- yellow or indigo
 
  If it's a Loop, Pentagon:
  small left leaning bud----- yellow or indigo
  small right leaning bud ---red, green or violet
  fat bud -------------------- orange or blue
 
  If it's a Triangle, Heart:
  small left leaning bud: ---- orange or blue
  small right leaning bud:---yellow or indigo
  fat bud ------------------- red, green or violet

STAGE 1: 2
Next you will need to try 3 different shapes and repeat all the above with them (That's assuming you haven't found all the right shapes yet).
There are 7 shapes, but if you have tested 6, the 7th will be wherever you still have gaps (in an ideal world)

STAGE 2
After trying out the shapes, you should know all the shapes you need to get the violet Candydevil (also the violet Cherrymole).
The next stage is to find the right colours.
Hunt for the shapes you need and make sure they are in the right positions (left, middle, right).
Any in colours you have already tried or as soon as a red, yellow or blue Candydevil comes along, you know you can harvest that candy (but don't leave yourself short of the 3 candies).  Keep the correct ones and hunt again for the remaining shapes.
Always note the colours you've tried whether correct or not.
Once all 3 shapes and colours are correct, you will be able to attract the violet Candydevil. It may take a while to come as you will also be attracting orange, green and indigo Candydevils (and possibly some Cherrymoles)

REALITY CHECK: It was easier to explain by assuming 3

That's the basic puzzle, so now to the whole thing.

I mentioned that you would also be getting the information on Cherrymoles while doing Candydevils.
In the same way - by using different foods, you can also be gathering the same information for all the other Candy critters.
Trying to solve 7 different puzzles at the same time is where it can get confusing.
At first every shape is new and there's something to be learned from every candy in our gardens (even if they attract nothing in any position, on any food type - that shape can be eliminated ) the first bits of information will be all over the place, but the gaps will start to fill up and hopefully it'll start to seem more orderly.

So at each of the Stages (and sub-stages) mentioned above, you would need to take 4 times as long as you do each with a different type of food. (Even if you have different foods out at the same time, you would need to take longer to give each type a good try-out)

Now you know which 3 shapes to use for each type of candy critter. (you might even know a few colours).
Next stage is to find the colours.

You could of course do this as soon as you know all the shapes for the violet of any candy critter, or wait until you know all of them before going for the violets.
I'd do one section at a time (or using a greenhouse- do a pair with the same food type), keep hunting for the 3 shapes for the type.

Each time a red of the type turns up, the colour of the candy on the left can be eliminated. If an orange turns up, the colour is right so keep that one.
Same with yellow (wrong colour) or green (correct colour) for the candy in the middle
Also with blue (wrong) and indigo (correct) for the candy on the right.
Keep replacing the ones with the wrong colour eliminating colours as you go until they are all correct.

Note that if you have filled gaps with an untried shape, it's worth checking that all the gaps you filled with it are actually correct  when you first need to use it.

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💛𝓢𝖕𝖗𝖎𝖓𝓴𝖑𝖊𝖉 𝖜𝖎𝖙𝖍 𝕭𝖑𝖊𝖘𝖘𝖎𝖓𝖌𝖘💛

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