For a reliable diagnosis of plant diseases and insect pests, it is very important to reproduce the original color of the object. But it is not certain by conventional color imaging systems. Multispectral imaging techniques are capable of providing additional useful spectral information of common pathological samples using image acquisition. The authors present a multispectral imaging system for the diagnosis. This system uses 16 narrow-band filters, a monochrome CCD camera, and standard illumination environment. Spectral match angle and color difference can be obtained through measurements and analysis of 8 Macbeth color patch using PR-715 spectraScan and multispectral imaging system. In addition, the color image and spectral reflectance of cucumber diseased leaves were reproduced using the multispectral imaging system. In the experiment, it was confirmed that the system realized good accuracy in the color reproduction and spectral reflectance reproduction from a limited number of color bands.