The Premier Ball (プレミアボール Premier Ball) was created for a special event. It is entirely white except for the band around the middle which is red. According to the official Pokémon Colosseum game guide, it has the same catch rate as a regular Poké Ball, Catch rate = 1 * (((( 4 * Max HP - 2 * HP ) * Catch Rate ) / Max HP ) + Status + 1 ) / 256.
But "it looks cooler." It can be obtained by purchasing 10 regular Poké Balls from a shop (Generation III onward).
NOTE: The accumulation of Premier Balls, when buying normal Poké Balls, does notstack. This means that when you buy any ammount of normal "standard" Poké Balls, so long as the total number bought is ten (10) or above, you get a single Premier Ball. I.e. buying 50 Poké Balls will not get you five (5) Premier Balls, but only one (1).