When you are on the level where you combine dyes and wool for the tailor to make your outfit, use these combinations to unlock the achievement (order does not matter, but save Green for last, since this is the color you want to complete the level):
- Red Dye + Blue Dye + Yellow Dye + Wool = Grey outfit
- Red Dye + Wool = Red outfit
- Yellow Dye + Wool = Yellow outfit
- Blue Dye + Wool = Blue outfit
- Red Dye + Blue Dye = Purple outfit
- Red Dye + Yellow Dye = Orange outfit
- Blue Dye + Yellow Dye = Green outfit
At this point the achievement unlocked, although you CAN create a white outfit by using only wool without any dyes.