Hmm, not sure where to begin. Like gtown mike, I separate pro teams from college teams. In addition, team colors or unis mean nothing to me in terms of my thoughts about a team. As a die-hard Eagles fan, there's no pro football team that I dislike more than Dallas. That said, Iowa, or any other college wrestling team you could think of, could wear the same uni as the Cowboys do (to the extent that a football team uni could be translated to a wrestling singlet), and it would have no influence on me. I only dislike a uni when it's worn by the team that I dislike.
Lastly, I think you're making a gross generalization about fans of Philadelphia sports teams concerning their feelings for Pittsburgh. Each fan has their own likes and dislikes. In terms of the actual sports/teams, the majority of Philadelphia fans, or at least those that were alive in the '70s, have always thought highly of the Steelers. As they're AFC and the Eagles are NFC, there isn't a lot of direct competition between the teams. A lot of Eagles fans have the Steelers as their favorite AFC team. In baseball, the Pirates have never been the Phillies top competitors, and while they are both NL teams they are in different divisions these days. The rivalry got a bit heated when both teams were good, but I don't think that's been the case since the late 70s. The Phils, with the exception of the '93 team, kind of stunk in the late 80s and most of the 90s, and didn't turn things around to the mid 00s. The Pirates were pretty bad during most of the Phils recent run, but last year the Phils stunk and the Pirates made the playoffs. There is more of a dislike between the Flyers' fans and the Penquins' fans, but that wasn't always the case. While both teams were part of the 1967 NHL expansion, the Flyers won 10 Division Championships, 6 Conference Championships and 2 Stanley Cups, before the Pens won their 1st Division Championship or Conference Championship (both in 1990-91). Things have been a tad more heated since then, and the Pens seems to have replaced some of the former least-favorite teams amongst Flyers' fans.