A process for producing a security feature for securing a value document, wherein said security feature exhibits a blue color upon viewing in transmitted light and a metallic yellow color upon viewing in incident light, said process comprising the following steps: a) printing, preferably by screen printing, rotogravure, or flexography, a UV-Vis radiation curable ink on a transparent or partially transparent region of a substrate of a value document to provide an ink layer; b) heating the ink layer obtained at step a) at a temperature of about 55 °C to about 100 °C for at least one second so that the ink layer exhibits a metallic yellow color upon viewing in incident light; and c) UV-Vis curing the ink layer obtained at step b) to form the security feature; wherein the UV-Vis radiation curable ink comprises: i) silver nanoplatelets having a mean diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, a mean thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and a mean aspect ratio higher than 2.0, wherein the mean diameter is determined by transmission electron microscopy and the mean thickness is determined by transmission electron microscopy; ii) from about 40 wt-% to about 75 wt-% of either a cycloaliphatic epoxide, or a mixture of a cycloaliphatic epoxide and one or more UV-Vis radiation curable compounds other than the cycloaliphatic epoxide; iii) one or more cationic photoinitiators; iv) a polyvinyl chloride copolymer containing at least about 69 wt-% of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of: hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25 wt-% of an organic solvent; the weight percent of ii), and vi) being based on the total weight of the UV-Vis radiation curable ink. a) printing, preferably by screen printing, rotogravure, or flexography, a UV-Vis radiation curable ink on a transparent or partially transparent region of a substrate of a value document to provide an ink layer; b) heating the ink layer obtained at step a) at a temperature of about 55 °C to about 100 °C for at least one second so that the ink layer exhibits a metallic yellow color upon viewing in incident light; and c) UV-Vis curing the ink layer obtained at step b) to form the security feature; i) silver nanoplatelets having a mean diameter in the range of 50 to 150 nm with a standard deviation of less than 60%, a mean thickness in the range of 5 to 30 nm with a standard deviation of less than 50%, and a mean aspect ratio higher than 2.0, wherein the mean diameter is determined by transmission electron microscopy and the mean thickness is determined by transmission electron microscopy; ii) from about 40 wt-% to about 75 wt-% of either a cycloaliphatic epoxide, or a mixture of a cycloaliphatic epoxide and one or more UV-Vis radiation curable compounds other than the cycloaliphatic epoxide; iii) one or more cationic photoinitiators; iv) a polyvinyl chloride copolymer containing at least about 69 wt-% of vinyl chloride; v) a perfluoropolyether surfactant functionalized with one or more functional groups selected from the group consisting of: hydroxyl, acrylate, and methacrylate; and optionally vi) up to 25 wt-% of an organic solvent; the weight percent of ii), and vi) being based on the total weight of the UV-Vis radiation curable ink. <EOS>