Is it a fair trade in this specific instance? You also can't, apparently, have coffee in a cup that's too close to the Coca-Cola shade of red. Does that help you know that your coffee isn't coke?
If we can start with the concept of trademarks being valid - they protect people as much as the company, it then comes down to whether a given product would mislead the typical consumer. If you run a nightclub called "M-C Donald's" then nobody is going to think it's a crappy burger joint. on the other hand if you use similar colors and/or font that mcdonalds an impartial person might think you're trying to trade on Ronald's name and mislead your public.
On the other hand if oyu run a hair salon called "British Hairways" with similar colors to the airline [0], I don't think a reasonable person would link the two.
There are of course going to be edge cases where people disagree. If you're making a red coffee cup that should be fine. If you're making it red with a swirly "Coffee" font which looks similar to the swirly Cocacola font that's probably not.
