In this study, a hemicyanine dye, trans-4-(4-(diethylamino)styryl)-1-ethylpyridinium bromide (DYE-BD), was synthesised and simulated. The maximum absorption wavelength of DYE-BD was calculated with the same basis set by using the Gaussian 09 software based on different methods, while time-dependent density functional theory was applied to simulate the maximum emission wavelength of the designed dye. The changes in enthalpy and Gibbs free energy were simulated at the b3lyp/6-31G(d) level, and energy changes in the luminescence process were assessed using mathematical methods. Furthermore, DYE-BD was used to colour acrylic fabric following the typical dyeing procedure for cationic dyes. The photostability of the synthesised dye was analysed using quantum theory and mathematical methods. The synthesised dye, analysed using the Ecological Structure Activity Relationships class program, had no toxicity to aquatic life, while the acrylic fabrics dyed with DYE-BD met the fluorescent orange requirements for background and combined performance materials according to the EN ISO 20471:2013 standard. 24 | TANG eT Al.