At the game mode screen, press L and R to activate the code entry screen, and enter the passwords bellow to enable their perspective cheats.

Password - Result

V1S10NS - 100 Gems
T4P10C4 - 200 gems
P0RT4L - Orange Mode
SPYR0 - Orange Spyro Mode
B41S0KV - Sheep Flame Mode
SH33P - Sheep Mode