To add onto what Valkita said, alternatively, you can get random colors (Edit: it is random colors that you get from guild town quests, not too sure if you get anything else from there or not) from doing guild town quests. As well, you can do repeatable quests for Alpaca Coins and try your chances at getting specific character dyes from the machines located in Tranquil Hill (or Highlands, but those ones in this case are irrelevant).