Talk to Regnbue the pallet maker in the little artist studio just east of Moonglow Trammel. She gives you clues leading Kezia the Recluse. Kezia can help you find the location of Iris the Goddess of Rainbows.
In Iris's shop you can buy one of Iris's Hue Pots from Arke the vendor. Arke also sells Dye Mordant needed to absorb the various hue powders to create Iris's special Equipment Hues.
To obtain the actual Hue Powders you will need to help combat Iris's pesky sisters. When the last of them is defeated you will be offered help finding the Hue Powder of your choice (there are eight of them and each can make two shades of its' hue.
When you have selected the Powder you seek . . . you will be given instructions to follow to obtain it.
1) Anyone can try this quest but you need to ne a great cook (120 = 65% chance) to successfully create one of Iris's Hues from the ingredients.
2) You will need a boat but do not leave it unattended (Drydock it when you can).
3) If a you accept this quest then Regnbue will not give it to any other player for 1 hour. I you accept this quest then Regnbue will not give it to you again for 4 hours.