Textile dyeing effluents with chemically stable dyes from crude oil and other hazardous chemicals are responsible for enormous environmental pollution worldwide. Microorganisms may provide alternatives to textile dyes, but production conditions of coloured metabolites are often poorly understood and need deeper investigation both for research (characterization of dyes, proof-of-concept) and for later industrial production. In this work, a photometric wellplate-based assay is developed to systematically investigate environmental influence factors for improved dye production in microorganisms. Challenges that are encountered and worked on: • Following dye formation and cell growth in parallel for normalisation • Increasing robustness by carefully choosing wavelengths and mode of sampling • Increasing reliability by choosing the right positive control