Two novel coumarin-indanone-based probes were designed, synthesized, and characterized by 1H NMR, 13C NMR, FT-IR, and LC-MS spectroscopy methods. One of these Michael addition type probes displays selectivity and sensitivity for the cyanide anion over the other anions. These dye showed rapid fluorescence and colorimetric responses and excellent selectivity for cyanide anion during the detection process within DMSO and in DMSO/H2O (9:1, v/v). By adding cyanide anion to the structure by the Michael mechanism, the double bond was broken and the electron transfer was stopped, thus the intramolecular charge transfer (ICT) was blocked by leaving the electron-withdrawing group out of conjugation. As a result, the hypsochromic shift was observed in absorbance and fluorescence spectra. The other dye showed selectivity but was not specific. In addition, the structural properties, frontier molecular orbitals, absorption spectra, cyanide addition mechanism, and MEP surface maps of the probes were obtained theoretically by using the DFT method.