Here is the full list of all 42 Love Colors: Paint with Friends achievements.
Paint whole picture
Color 100 pixels in total
Color first pixel of any picture
Use Fill tool 10 times
Use Bomb tool 10 times
Finish all pictures in a collection
Fill at least 50 pixels with one use of Fill tool
Finish big picture without quitting
Finish all pictures in Africa collection
Finish all pictures in Animals Collection
Finish all pictures in First collection
Finish all pictures in Birds collection
Finish all pictures in Second collection
Finish all pictures in Brazil collection
Finish all pictures in Canada collection
Finish all pictures in China collection
Finish all pictures in Christmas collection
Finish all pictures in Cities collection
Finish all pictures in Clothes collection
Finish all pictures in Drinks collection
Finish all pictures in Farm collection
Finish all pictures in Flowers collection
Finish all pictures in Food collection
Finish all pictures in Food Dlc collection
Finish all pictures in Fruit collection
Finish all pictures in Games collection
Finish all pictures in Halloween collection
Finish all pictures in Hard collection
Finish all pictures in Emotes collection
Finish all pictures in India collection
Finish all pictures in Insects collection
Finish all pictures in Kitchen collection
Finish all pictures in Masks collection
Finish all pictures in Monsters collection
Finish all pictures in Poland collection
Finish all pictures in Sports collection
Finish all pictures in Sweets collection
Finish all pictures in Vehicles collection
Finish picture without making mistakes
Finish all pictures from base version of the game
Use Fill tool for the first time
Use Bomb tool for the first time