Cadbury has lost the latest round of a fight to register a purple chocolate wrapper as a trade mark.
Last year the chocolate giant won a High Court row with rival Nestle over who could use a particular shade of purple.
But today the Court of Appeal overturned Judge Colin Birss's decision - made after a High Court hearing in May 2012 .
Three appeal judges ruled that the Cadbury claim lacked "specificity" and did not comply with "requirements for registration".
"To allow a registration so lacking in specificity, clarity and precision of visual appearance would offend against the principle of certainty," said one appeal judge, Sir John Mummery.
"It would also offend against the principle of fairness by giving a competitive advantage to Cadbury and by putting Nestle and its other competitors at a disadvantage."