1. An image processing apparatus that adjusts a color of image data, comprising: an obtaining unit configured to obtain a viewing angle of a first observation target and a viewing angle of a second observation target; and a color correction unit configured to perform correction of colors of image data representing the observation targets by using the viewing angle of the first observation target and the viewing angle of the second observation target which are obtained by the obtaining unit, wherein the color correction unit performs the correction using correction parameters corresponding to the viewing angles, and the color correction unit converts a colorimetric value obtained by measuring the color of the first observation target with a measuring method using 2 degrees or 10 degrees as a measuring viewing angle, the measured colorimetric value being converted by using a first color correction parameter obtained from a correction parameter corresponding to the viewing angle for the measuring method using 2 degrees or 10 degrees as a measuring viewing angle and a correction parameter corresponding to the viewing angle of the first observation target, a second color correction parameter obtained from the correction parameter corresponding to the viewing angle of the first observation target and a correction parameter corresponding to the viewing angle of the second observation target, and a third color correction parameter obtained from the correction parameter corresponding to the viewing angle of the second observation target and the correction parameter corresponding to the viewing angle for the measuring method using 2 degrees or 10 degrees as a measuring viewing angle.