Abstract: In a method for transforming a color signal, a target output color signal component (X, Y, Z) is transformed into an input signal component (B, G, R) by referring to a look-up table, and a target output color signal component, which is not stored in the look-up table, is transformed into an input signal component by an interpolating process. In an output color signal space, a local coordinate system is set by using a successive approximation process, and a desired output color signal component is subjected to linear interpolation in the local coordinate system. A three-dimensional interpolating process is thus carried out quickly and accurately and over the entire color reproduction range.