How do you get the purple pikmin in pikmin 1?

The easiest way to get white and purple Pikmin is to go into easy caves, find the Candypop Buds and transform Pikmin, then get out. Keep in mind that Candypop Buds do not reappear in the same day after leaving a cavern.

Emergence Cave in the Valley of Repose is best for purple Pikmin, and the White Flower Garden in the Awakening Wood is best for whites. Relatively easy caverns that can be used to get white and purple Pikmin are the Snagret Hole in the Valley of Repose and the Citadel of Spiders in the Perplexing Pool.