Viva Piñata

Arocknid
Blue: Bluebell flower
Pink: Water Lily flower
Orange: Jack 'o Lantern

Badgesicle
Red: Apple
Blue: Bluebell flower
Fuchsia: Jar of Honey + Water Lily flower

Barkbark
Green/Yellow: Bannana Split
Pink: Medicine
Green: poison ivy flowerhead

Bonboon
White: Orchid
Blue: Bluebell flower
Yellow/Green: Watercress seed + Bird of Paradise seed

Bunnycomb
Yellow: Pumpkin
Pink: Water Lily flower
Light Green: Gooseberry seed

Buzzenge
Yellow: Buttercup
Blue: Bluebell seed
Pink: Bottle of Medicine

Buzzlegum
Green: Venus Pinata Trap flower
Bright Pink: Bottle of Medicine
Purple/White: Gem tree seed

Candary
Pink: Water Lily seed
Blue: Bluebell
Light Green: Gooseberry fool

Chewnicorn
Pink: Water Lily seed
Yellow: Ear of Corn
Blue: Water Lily flower + Bluebell flower

Chippopatamus
Pink/Purple: Water Lily seed + Bird of Paradise flower
Yellow/Green: Watercress flower + Mushroom
Pink: Bottle of Medicine + Jar of Jam

Cinnamonkey
Red: Chili
Purple: Blackberry seed
Pink: Water Lily flower

Cluckles
Blue: Bluebell seed
Green: Oak seed
Pink: Bottle of Medicine

Cocoadile
Pink: Water Lily seed
Light Blue: Bluebell
Yellow: Buttercup seed

Crowla
Pink: Water Lily
Orange: Bird of Paradise
Blue: Bluebell seed

Doenut
Orange: Jack O' Lantern + Ear of Corn
Green: Oak seed
Purple: Thistle flower + Gooseberry fool

Dragonache (note: can't be changed after hatching)
Green: hatch egg on Grass
Blue: hatch egg in Water
Brown: hatch egg on Fresh Soil
Orange: hatch egg on Dried/Cracked Dirt

Dragumfly
Blue: Bluebell seed
Green: Poison Ivy flower
Orange: Pumpkin

Eaglair
Yellow: Buttercup seed
Blue: Bluebell seed
White: Bottle of Milk

Elephanilla
Blue: Bluebell
Orange: Buttercup
Red: Poppy seed

Fizzlybear
Bright Gold: Sunflower seed
Orange/Pink: Carrot
Green: Watercress seed

Fourheads
Blue: Bluebell flower
Yellow: Honey
Pink: Bottle of Medicine

Fudgehog
Red: Chili
Blue: Bluebell seed
Green: Poison Ivy flower

Galagoogoo
Yellow: Sunflower
Light Purple: bread
Green: Poison Ivy flower

Gooba
Blue: Bluebell
Black: Tulip seed
Pink: Water Lily seed

Horstachio
Green: Watercress flower
Blue: Bluebell flower
Red: Chili seed

Jameleon
Blue: Bluebell seed
Red: Carrot Cake
White: Orchid flower + Bottle of Medicine

Juicygoose
Yellow/Pink: Banana
Pink/Orange: Water Lily seed + Bird of Paradise seed + Poppy flowerhead
Green/Yellow: Oak seed

Kittyfloss
Pink: Bottle of Medicine
Blue: Bluebell
Pink/White: Water Lily flower

Lackatoad
Blue: Bluebell
Pink: Water Lily seed
Yellow: Banana Tree seed

Lickatoad
Purple: Bluebell seed
Red: Apple + Carrot
Green: Gooseberry + Bluebell flower

Macaraccoon
Pink: Water Lily seed
Yellow: Mushroom
Blue: Bluebell seed

Mallowolf
Purple: Blackberry
Pink: Water Lily seed
Blue: Bluebell seed

Moozipan
White: Sandwich
Yellow: Banana Tree seed
Pink: Waterlily seed + Snapdragon seed

Mothdrop
Yellow: Daisy flowerhead
Blue/Orange: Bluebell seed + Turnip + Carrot
Green/Red: Pumpkin + Watercress flower

Mousemallow
White: Cheese
Bright White: Bluebell + Daisy
Off White: Daisy + Gooseberry seed

Newtgat
Blue: Bluebell flower
Orange: Bird of Paradise flower
Pink: Water Lily seed

Parrybo
Orange: Venus Pinata Trap flower
Yellow/Green: Oak seed + Wedge of Cheese
Blue: Bluebell flower + Nightshade berry

Pigxie
Blue: Bluebell seed
Green: Gooseberry Fool
Fuchsia: Gem Tree seed + Waterlily flower + Poppy flower

Ponocky
Pinkish Purple: Bread
Pink: Water Lily flower
Blue: Bluebell seed

Pretztail
Blue: Bluebell
Pink: Water Lily
Green: Gooseberry fool

Profitamole
Pink: Water Lily seed
Green: Watercress
White/Blue: Nightshade seed + Bluebell seed

Pudgeon
Blue: Bluebell
Purple: Jar of Jam
Green: Gooseberry seed

Quackberry
Blue: Bluebell seed
Pink: Water Lily flower
Orange: Bird of Paradise seed

Raisant
Purple: Bluebell seed + Blackberry
Yellow: Sunflower
Pink: Water Lily

Rashberry
Green: Watercress seed
Red: Poppy seed
Purple: Nightshade berry

Reddhott
Blue: Bluebell seed
Pink: Water Lily flower
Red: Carrot Cake

Roario
Pink: Bottle of Medicine
Blue: Bluebell seed
Yellow: Sunflower seed

Salamango
Green: Gooseberry
Yellow: Banana
White: Bottle of Milk + Nightshade seed

Shellybean
Blue: Bluebell flower
Green: Gooseberry
Yellow: Ear of Corn

Sherbat
Bright Blue: Bluebell flower
Yellow: Sunflower seed
Red: Chili seed

Sparrowmint
Green: Watercress flower
Pink: Water Lily flower
Purple: Thistle flowerhead

Squazzil
Pink: Water Lily seed
Purple: Snapdragon blossom
Green: Watercress seed

Swanana
Purple: Snapdragon flowerhead
Green: Gooseberry seed
Pink: Bottle of Medicine

Sweetooth
Purple: Bluebell
Yellow: Sunflower
Pink: Bottle of Medicine

Syrupent
Gold: Buttercup flower
Blue: Bluebell seed
Pink: Bottle of Medicine

Taffly
Green: Poison Ivy flowerhead
Yellow: Buttercup seed
Purple: Blackberry seed

Twingersnap
Purple: Snapdragon seed
Orange: Bottle of Medicine
Yellow: Venus Pinata Trap

Whirlm
Purple: Turnip
Red: Water Lily seed
Green: Watercress seed

White Flutterscotch (note: variants also changes species)
Red: Poppy flower
Green: Watercress flower
Blue: Bluebell flower
Pink: Water Lily flower
Black: Tulip flower
Brown: Bullrush
Yellow: Buttercup flower
Orange: Bird of Paradise flower
Purple: Thistle flower

Zumbug
Blue: Bluebell seed
Pink: Water Lily seed
Yellow/Orange: Banana Split & Carrot Cake

These are all the examples of pinatas

I got this guide off of x360a variants list by Crash

For this achievement you will need to make 20 different variants of pinata, variants are simply changing a certain pinatas color by eating certain things, each different color counts as a variant. Here are some examples:

Bunnycomb

- Water Lily flower = pink
- Gooseberry Seed = green
- Pumpkin = yellow

Cluckles

- Bluebell Seed = blue
- Oak Seed = green
- Bottle of Medicine = pink

Fudgehog

- Chili = red
- Bluebell Seed = blue
- Poison Ivy Flower = green

Horstachio

- Watercress Flower = green
- Bluebell Flower = blue
- Chili Seed = red

Kittyfloss

- Bottle of Medicine = pink
- Bluebell = blue
- Waterlilly = pink/white

Lickatoad

- Bluebell Seed = purple
- Bluebell Flower and Gooseberry = green
- Apple and Carrot = red

Moozipan

- Waterlily Seed and Snapdragon Seed = pink
- Sandwich = white
- Banana Tree Seed = yellow

These are only a few examples, as all the pinatas have variants (except the Dragonache), I just listed some of the more common pinatas.