Compositions that include bis(glyoxime)-transition metal complexes bound to metal oxide solid supports are provided. In some embodiments the compositions include nickel dimethylglyoxime and the metal oxide supports can be alumina or silica. These compositions can be used to make a colorimetric moisture-indicating sensor that changes visible reflection spectrum quantitatively and reversibly according to the amount of moisture in contact with the sensor. Also provided is a method of detecting moisture using the provided compositions.