Once you've placed the Rainbow, you'll be able to jump right into the upgrade process, which asks you to collect different colors and amounts of Shamrocks for every level. For the first upgrade (Level 1 to Level 2), you'll need to collect six Shamrocks: two each in green, red and orange. These can be earned by asking your friends to send them to you, or by purchasing them outright for City Cash. You can also earn these items at random by collecting from Irish themed buildings, as there have been plenty of them released in the store to go along with this event.
As you upgrade your Rainbow, you'll get closer and closer to Level 6, the final level, where you'll be rewarded with the ultimate prize: a Pot of Gold containing 1 million coins. It should be noted, however, that things are working a bit against you here, as your inventory of Shamrocks will be reset when upgrading to each new level (as of this writing). That is, you can't simply have 25 Green Shamrocks in your inventory during your first upgrade and then use that supply until they run out - the second you upgrade to Level 2, your 23 extra Shamrocks will be automatically deleted. That being the case, you'll need to continually ask your friends for help. Unfortunately, the Shamrocks you'll receive from your friends are random, as you can't ask for a specific kind. You can, however, ask your friends to send you Mystery Shamrocks from the game's free gifts page, to hopefully quicken the process.
You'll have 22 days to fill out the entire Rainbow and receive your 1 million coins in the end. Remember, you can earn extra Shamrocks by collecting from your new themed buildings, and we'll bring you a guide to building those particular structures just as soon as we can. Stay tuned! UPDATE: You can check out our full guide to the buildings you'll need to build for this event right here.
Are you excited to build your own Rainbow in CityVille? Is the 1 million coin prize enough incentive for you to go through this lengthy upgrade process? Sound off in the comments.