Rainbow flags will add color to Saturday's Three Rivers Arts Festival and Bucs game scenes when local gay, lesbian, bisexual and transgendered Pittsburghers celebrate PrideFest 2004. PrideFest 2004 is set for noon to 6 p.m. on the North Shore. The event is expected to draw as many as 2,000 revelers to the scheduled parade, festival and Pirates baseball game.The day will be capped off by Pride Day at PNC Park where representatives from the gay, lesbian, bisexual and transgendered community will hurl the ceremonial first pitch, kicking off play between the Pirates and the Seattle Mariners, Sette said.