Hello! We are delighted to see that you are interested in joining the competition, Simonian :D
First of all, thank you so much awergh for your swift reply and assistance, we really appreciate it!
As awergh pointed out, Rainbow Island is an arcade game. Using your imagination, the point of the gesture is to include an easter egg of this game in your own game as a feature, item, enemy, playable character, color palette... Anything that references the game and it is explained on your game user manual. For example, you can see that in the example game page the gesture is an enemy that represents the main character of Chicago's 30.
For more information about the gesture or contest, please see the contest rules.