An anthraimidazoldione-based chromogenic probe is synthesized that exhibits dual absorption bands in pH 7.4 PBS buffer due to n→π* transitions and intramolecular charge transfer (ICT). Coordination with Ni²⁺ causes a blue shift in the ICT band (492 nm → 410 nm) and changes in solution color from red to yellow, indicating strong interaction with a 1:1 binding stoichiometry. Further, the insitu formed Ni²⁺ complex shows highly selective ratiometric response towards histidine, with a detection limit of 12 µM. Histidine addition restores the ICT band at 502 nm with restoration of original red color of native probe. Reversible interaction with histidine confirms the mechanism of Ni²⁺ sequestration. Comparative studies with Cu²⁺ revealed similar histidine-induced absorbance restoration, but in lesser extent due to lower binding affinity. Moreover, the Ni-complex can successfully differentiate proteins based on numbers of their histidine residues.