The biological study identified three fungal species (Aspergillus fumigatus, Aspergillus Niger, and Aspergillus Flavus) and three bacterial genus (Pseudomonas taetrolens, Bacillus subtilis, and Serratia rubidaea) as the most effective in altering the colors of Egyptian blue and Egyptian green pigments. Laboratory experiments confirmed that marjoram oil is the optimal biocide for both fungi and bacteria due to its strong antibacterial and antifungal properties. It was applied as a solution and had no adverse effects on the pigment materials on the stela.In summary, specific fungal species and bacterial genus were found to have a significant impact on the pigments' colors. The use of marjoram oil as a biocide proved effective without harming the stela's pigment materials.