Trademarks are only supposed to be infringing if they're creating confusion in the marketplace. The boundaries of a trademark are supposed to be within a single "industry". "American Airlines" might be able to sue rival airline "American Air" but not compressed gas supplier "American Air". In reality I'm pretty sure that most of these cases are decided not on the merit of the claims but rather the threat of financial ruin on the lesser funded party and that's how we got to corporations "owning" colors.