Same reason that at one point in the game Hogan is in Black and White, and later he goes back to Red and Yellow.
They encompase a variety of looks in the game.
Druggy man vs. Len Stormrock.
*Wonders how many people get that second reference.*
Anyway, Lance Storm is a prime reason why some people should wear long tights.
Brock owes HHH nothing but a BRUTAL BEATDOWN!
BROCK! HIT HHH WITH THE FORCE OF HOGAN, ROCK, AND UNDERTAKER COMBINED! YOU STOLE THEIR SOULS AND POWERS, NOW STEAL HHH'S BACKSTAGE POWER!
YOU ARE THE MEGAMAN OF WRESTLERS!