The blue on blue floral print on the CAROLUS longsleeve shirt is a mix of tulips from Amsterdam and the Indigofera plant. Indigofera is where indigo comes from, the dye used to make jeans blue. The combination of tulips and Indigofera symbolises the brand name Amsterdenim. The name Carolus refers to the Botanicus Carolus Clusius who introduced the tulip in the lowlands (The Netherlands and Belgium) in the 1600's. Did you know that nowadays, The Netherlands is the largest exporter of flowers in the World? Also available as short sleeve shirt! Original artwork by Dutch designer Marian Vrij.