Feels a bit militant in green and black, and a bit depressing in rust. I hate to say I like the blue and gold the best, however I think blue and black could work and it would also reflect the memorable horses featured on the current flag. I also immediately interpreted the stars as Philly and Pittsburgh with the "the rest of the keystone state" in between. I'm also not a huge fan of the stripe directly on the fly end. Maybe it would be easier to just make it two stripes to symbolize the second state, with the keystone in the top left? I'd be curious to see it with two horizontal stripes instead of two vertical as well.