A lot of logos are even trickier to use, words can be considered to be in general usage, but companies regularly trademark specific colour and font combinations. Cadbury's even tried to trademark the colour purple recently. Normally with a trademark though the mark is specific to a particular type of goods or service. You can have two companies with the same name e.g. Corus which was used by both the steel company and a hotel chain I once worked for, but the two companies can't sue each other for breach of trademark because the trademarks have to designate specific industries, or at least that is the case in the UK
