A card, comprises an electrically non-conductive substrate; a first predetermined pattern of electrically conductive material applied on said electrically non-conductive substrate; and an electrically non-conductive covering layer applied on said electrically conductive material arranged on said substrate such that said first predetermined pattern of electrically conductive material is covered; said card further comprises a second predetermined pattern in a predetermined grey percentage applied on said electrically non-conductive substrate, said predetermined second pattern being the negative of said first predetermined pattern, and said electrically non-conductive covering layer is also applied on said second predetermined pattern such that said second predetermined pattern is covered, and the greyness of said second predetermined pattern has been determined such that the colour of the electrically non-conductive covering layer is uniform.