First go to the petpet park mall. Go to the the grooming store.
Find the rainbow colour bottle and buy it. Then go to Groomtopia in
Fashion Field. Use the colour bottle and you have a rainbow
Go to the mall and buy a rainbow colour bottle.It costs 200 nick
cash.Buy it.Go to Fashion Field.Go to Groomtopia.Click on Colour
Changing Station.Select the rainbow colour bottle. There you go!
Hope I helped!