a method for coloring fibers or fibrous materials where the fibrous material is initially chemically pretreated in order to achieve natural / white color for the fibrous materials . next the pretreated fibrous material , a polymer base , and the colorant concentrate are combined under suitable conditions to form a biocomposite mixture . the chemical pretreatment of the fibrous material prevents damage from being done to the fibrous material , such that the fibrous material retains its strength enhancing properties when combined with the polymer to form the biocomposite mixture . additionally , the chemical pretreatment enables the fibrous material to chemically and mechanically bond with the colorant when combined into the biocomposite mixture .