I tried placing the sign in various configurations with flower colors, nothing seems to help. All of the requests ask for colors that would require you to mix them, but i can't find a mechanic in the game that allows for it. Seems like it could be fun.

The cool downs on new requests just seems like an arbitrary way of slowing down the player's progress. When you're just working on levelling up your flowers, completing quests will gradually go faster as your growth and gain stats increase and then it gets kind of tedious to have to wait 90 seconds between new requests. I don't see any reason to even have cool downs on them, but maybe at least cut the time in half?...

It seems the only way to see your current stats on any color flower is to plant it. Would be handy if you could see it in your plants list too without having to plant the flower first.