Provided herein is an inkjet ink composition for printing irremovable color trace marks on polymer substrates. The composition disclosed herein comprises a surface colorant, a hydrophobic colorant capable of staining the polymer substrates disclosed herein, a hydrophobic colorant carrier which provides good solubility for the hydrophobic colorant, a binder and an ink solvent system. Printing with the composition disclosed herein on multilayered plastic packaging provides a double layered print. The surface colorants can be removed by an organic solvent, while the hydrophobic colorant can stain the nonporous substrates, giving a watermark of the surface print or an inner layer trace marks, which are highly resistance against chemical and physical stress. The composition disclosed herein also allows color tuning of the trace marks. Attempt to remove the printed information by any physical or chemical means will leave irremovable color trace marks, thus allowing consumers to detect tampered goods.