By using your own Pokemon, whether it be from Yellow, Blue or Red, can not only allow you to play with your own Pokemon; it can allow different colors of Pokemon, too. By naming your Pokemon a certain name, they may appear to look different when using them in Pokemon Stadium. Here is a list for many of those special names and the Pokemon they refer to. The Pokemon's custom name is on the left, while the actual Pokemon and their description of its newly gained looks are on the right.
HYDRO PUMP - Dark blue Gyarados
PIKACHAIN - Green Pikachu
THUNDER - Dark orange Jolteon
THUNDER - Dark orange Pikachu
BASSFAIRY - Green eared Clefairy with light peach body
BULBACE - Yellow eyes and tongued Bulbasaur
PUNCHMAN - Green Hitmonchan
SLEEPY - Light green Snorlax
SEY-CHAN - Darker Chansey
TONSTOR - Darker Magneton
EKANACT4 - Lighter Ekans with lime green mouth and a stripe down its belly
NIDOACT2 - Purple bodied Nidoqueen with green ears or vice versa
METRONOME - Neon Yellow Pikachu
PSYCHIC - Red Mewtwo
ATTATA - Pinkish Rattata
ONIXACT4 - Crystal colored Onix
FEARASH - Darker Fearow
POLIACT2 - Greenish turquoise Poliwhirl
CATERPY - Brownish Caterpie
ODDY - Oddish with different colored leaves
NIDON(female sign) - Female Nidoran that is green with purple mouth and ears or vice versa
BLADE - Teal colored Scyther with gray scythes and deep purple eyes
ZEPHYR - Tannish Pigeot
SPARKY - Goldish Pikachu
WARMARSH - Aquamarine Blastoise with tan shell
BLAZE - Lighter Charizard with teal wings and navy blue eyes
FLORA - Blue bodied Venasaur with jade leaves, fuschia flower, and a beige stem of flower
VINCENT - Purple Haunter
ELECTRACE - Electrode with purple-red bottom half
VICTRACE - Orangeish brown Victreebel with yellow leaves and yellow spots
PSYDANCE - Dark Yellow Psyduck
SOLAR WAVE - Red eyed Butterfree with purple body and blue feet
DIG - Turquoise blue Geodude
ROCK SLIDE - Turquoise blue Geodude
SUPERSONIC - Purple winged Zubat with luminous green body
HAZE - Purple winged Zubat with luminous green body
CLAM - Blue Shellder
HYDRO PUMP - Dark blue Lapras
MAGIMER - Orange or dark red Magikarp
LYGAST - Gold tongued Gastly
KOFSTOR - Red Koffing with green sign
FINGKOF - Blue Koffing
MAN-TIS - Orange eyed Butterfree with purple body and blue feet
ACID - Purple eyed Tentacool with a greenish blue body
DRAGONZORD - Dark red Charmander
WRAP - Yellow Bellsprout
RAZOR-LEAF - Orange petaled Venasaur with royal blue body
THUNDA - Lime green Zapdos
CASPER - Turquoise blue Haunter
FIRE-BLAST - Orange flamed Magmar with neon yellow body.
Keep in mind that these color changes are NOT permanent, and will be gone if you change your Pokemon's name.
