Shivonne and Barney The Ruler Of The House 1 month, 3 weeks ago
I am currently in the middle of this challenge and I find my trusty spreadsheet works for me. I keep track of number of each colour I have seen and what I want to see.
I also freeze while out and about hunting (see tip above by L and Elfin) as I always fall over multiples of colours I don't want. I have flipped only 1 flower so far and it was quite easy to fix given it was Orange which turned a flower to Yellow. On the harder to get colours (Green, Blue, Indigo, Violet) you definitely want to be careful and this is why I definitely recommend freezing your garden while you are out hunting. Once you find an alert for the colour you are after, dash back and unfreeze your garden.
I suggest staying away from hunting in the Rainbow Gardens as you never know what colour you are going to get. But if you like to live life on the edge, go for it!
This is a lovely, fairly relaxed challenge to do and the players I have met along the way are like a little community who help each other along.