White Apricorn---Fast Ball; Good for catching Pokemon that try to escape from battle quickly.
Red Apricorn-----Level Ball: If your Pokemon's level is significantly higher than the wild Pokemon's, it will be an easy catch.
Blue Apricorn----Lure Ball: Good for catching Water types when fishing.
Pink Apricorn----Love Ball: If the wild Pokemon's gender is opposite that of your Pokemon's you will have an easier catch.
Black Apricorn---Heavy Ball: Big enough to catch heavy Pokemon like Snorlax.
Green Apricorn---Friend Ball: Pokemon caught with Friend Balls will become very attached to their trainer. Good for Chansey (if you want it to evolve into Blissey).
Yellow Apricorn--Moon Ball: Good for catching Pokemon that evolve with Moon Stones, like Clefairy and Jigglypuff.