Some one posted a comment to the effect that tool use may be the determining factor in the colour of Wonderful you will obtain as a prize at any Festival Contest in IoH. I am afraid that I misunderstood at the time. In Island of Happiness, experience with a tool does not lead to any upgrades. I therefore did not feel that your character's level of experience with any tool could be a determining factor.
According to comments posted here, as tool use does increase your Farming Degree points, it is relevant as the last two digits of your current Farming score determine the colour of the Wonderful.
Thus, tool use would have an effect. It seems to me that the system I employed is as good as any as there is no Accessory that displays points. Save your game before you enter the Meadow. If you do not receive the colour that you want, reload, use your Tools and then re-enter.
There is an order in which the colours will appear:
Lowest Score to Highest:
Any one recognise the order? It's the same order as the Coloured Wild Grasses appear in your Farm Menu as well as the same order in which the Harvest Goddess will give you the Recipes for the Coloured Curries.
Thanks, guys, for your comments!
Incidentally, it does not require much tool use at all to change the colour of the Wonderful. A method that can profit you as well as changing the colour of the prize is to go to the entrance to the Meadow at 10.00 a.m. Stand on the near bank of the river, to the left of the bridge that leads to the Meadow and fish briefly. You should be able to judge how many casts of the Rod to cycle through each of the Wonderfuls with a little practice. With an ordinary tool, it varies between 10 and 15 uses for each change in colour.