For this achievement you need to make 5 different piñata species become a resident to your garden.
A piñata which is not currently a resident of your garden will appear in black and white, the first species you encounter in the game don't require much to make them take up residence in your garden, for example Whirlms only require you to have a certain amount of soil or grass in you garden, once you've attracted a few Whirlms into your garden then Sparrowmints will start to take notice, the entire game is based around this mentality, you always need something to attract a piñata to your garden, you'll always need to go a step further to make them join your garden.
When a piñata visits your garden you can move your cursor over it and press "Y", doing this will bring up the information about that species of piñata, use this to work out what you need to do to make them join your garden.
For information specific species and what they require to visit your garden and take up residence in your garden please see here;
http://http://pinataisland.info/viva/Species, that's a complete database with information on every piñata from both games, use the search feature to find a specific species and you'll be presented with all the information you need to make them want to visit your garden and join it!