<p>Chromium(VI) is considered to be a potent carcinogen by several health regulatory agencies. Its primary source is discharge from industries such as steel mills and tanneries. Excess amounts in the human body are a health concern for people overexposed to it. Therefore, monitoring chromium poisoning is paramount for those working in these industries. The present study focuses on colorimetric sensing of chromium in the Brahmaputra water using the 1,5-diphenylcarbazide (DPC) route. DPC selectively forms a colorimetric complex with chromium, confirmed by an ultraviolet–visible (UV–Vis) spectrophotometer at 543&#xa0;nm. Akin to UV–Vis absorbance, the electric resistance of the colorimetric complex was measured using a custom-designed prototype consisting of a light-emitting diode–light-dependent resistor (LDR). The terminals of the LDR were connected to a digital multimeter. The readings of the different spiked samples obtained from the multimeter were used to develop a calibration plot, which exhibited excellent linearity, with an <i>R</i>² value of 0.99. The limit of detection was calculated and reported to be 0.014&#xa0;mg L⁻¹, which falls within the World Health Organization’s recommended threshold value of 0.05 mg L⁻¹. The results were also validated with a UV–Vis spectrophotometer, proving the prototype’s efficacy and its potential for translation into a point-of-care testing device for healthcare applications.</p> Graphical Abstract <p></p>