One of Rainbow Island's most infamous and difficult-to-achieve bonuses is that of collecting one of each of the colored gems (red, orange, yellow, green, light blue, dark blue and mauve). Gems are awarded when a player collapses a rainbow onto certain enemies and the color of the gem awarded is dictated by WHERE on the screen the enemy is when it's killed. The screen is split into several invisible vertical 'bands' of color; when a gem falls, its color is determined by the 'color' of the area into which it fell. Now all you have to do is gauge carefully where the dead enemy will fall to create the gem color of your choice.
Title Screen Cheats : These codes can be typed in at the title screen (while the rainbow is cycling through its colors). They are given to you in the secret rooms and give you the effect of the item in that room if you use them. When you put your coin in, an item should appear in the bottom left corner, depending on which cheat you used. This not only awards you the life and Bonus Gem, it also grants you access to a magical secret room. When you reach the end of the level, a silver door appears. You DON'T have to fight the Boss.
Permanent fast running - Rainbow, Left, Right, Rainbow, Jump, Start, Rainbow, Jump
Permanent double rainbows - Right, Jump, Start, Rainbow, Jump, Start, Rainbow, Right
Permanent fast rainbows - Start(x3), Left(x2), Right(x2), Start
Hint A, The riddle of the silver door - Rainbow, Jump, Rainbow, Jump, Rainbow, Jump, Right, Start
Hint B, The secret of the big diamonds - Left, Jump, Left, Start, Left, Rainbow, Left, Start
Hint C, The riddle of the 3 mirrors - Start, Jump, Rainbow, Left, Right, Jump, Start, Right
Continue after fifth Island - Left, Rainbow, Start, Jump, Right, Left, Jump, Left
All hidden items are money bags (10000 pts) - Right(x2), Left(x2), Rainbow(x2), Jump, Start
Both above two - Right(x4), Start, Rainbow, Start, Jump
10m points - Start, Right, Rainbow, Jump, Start, Left, Start, Rainbow
Better Bonus : Make sure the second to last 2 digits of your score are the same when you reach 'goal in', this will make the chest contain a better bonus item (eg. : reach goal in with a score of xxxx11x).