This study presents a novel dual-modal approach for glutathione (GSH) detection using blue and yellow dual-emission carbon dots (BY-CDs) and bromothymol blue (BTB) at pH 8.0. The method employs both colorimetric and fluorometric detection modes, offering a new perspective on GSH quantification. BTB's blue coloration induces selective fluorescence quenching of the CDs' 610 nm emission peak, with minimal effect on the 445 nm peak. Upon GSH addition, the quinonoid structure (blue color) of BTB transforms to its benzenoid form (yellow color). This transformation triggers fluorescence restoration at 610 nm and significant quenching at 445 nm, enabling ratiometric fluorescence analysis (F₆₁₀/F₄₄₅). Concurrently, colorimetric detection is also ratiometric, based on measuring the ratio between the emerging yellow color peak (435 nm) and the decreasing blue color peak (618 nm) (A₄₃₅/A₆₁₈). The state-of …