Two simple chromogenic indicators (4) and (5), containing different supernucleophilic moieties, have been synthesized. Upon phosphorylation with two chemical warfare agent (CWA) simulants, a hypsochromic shift of approximately 50 nm is observed in an NaOH–DMSO solution. The oximate supernucleophile was found to be a better supernucleophile than the hydrazone moiety. Two X-ray crystal structures were obtained from unexpected synthetic side products obtained in this study. These will also be discussed.