This paper reveals one of the advantages of using multiprimary display, which can utilize the degrees of freedom. A spectral-approximation method, which was already proposed, is one of the methods concerning this advantage. This method is based on minimizing the difference between the spectrum of the original object and the reproduced spectrum under the constraint of tristimulus match for the CIE standard observer. We can expect some reduction of the color mismatch for any CMF. However, visual evaluation for actual images has not been reported until now. Therefore, we made a visual experiment to evaluate the spectral-approximation method using actual images, which contain many colors and shadings. We also present a novel algorithm for the spectral-approximation method.