Provided is a security thread to provide protection against forgery, which is embedded in paper or documents. The security thread comprises an elongate substrate with first side and second side and optical variable structures on first and second side of the elongate substrate with a thin film interence structure. The optical variable structures are arranged with separation interference filters inparallel and spaced with each other, with visible patterns having visible color shifting property such that they are identified visually, in reference to foreground or background of different colors.