Here's a suggestion. Regular Bombard Battle in Gridania yields Green Ash. Ul'dah yields Red Ash. Limsa yields Blue Ash. Convert 50 ash into a Yukata (60% chance) or a Halter (25% chance) or a Tanga (15% chance) of the SAME COLOR as the ash.
Add: Lord Bombs in dungeons in Gridania yield White Ash. Lord Bombs in dungeons in Limsa yield Black Ash. Lord Bombs in Ul'dah yield Gold Ash. Convert these same as above into items of the same color (Black Ash yields Black items. White Ash yields white items. Gold Ash yields gold items.)
Some years or under special circumstances or maybe using a combination of ash colors you should be able to get silver items, yellow items, purple items, pink items. The White Yukata, Black Yukata, and Gold Yukata should have better designs, like real ones.