When image processing operations are performed on color images, it is normal that the production of out-of-gamut pixels is not prevented. The gamut mapping may reduce the effect of the image processing algorithm. In this paper we propose a generic method that allows grey image processing for lightness processing on color images without exceeding the limits of the gamut of the technique or device.In the proposed method the lightness processing is a function of the color of the pixel in question, the desired lightness change and a maximum and minimum lightness change per pixel. This maximum and minimum depend on the position of the pixel in the gamut of the output device and the relation between the lightness change and the chroma change. The hue of all pixels is kept constant. The monotonic character of the lightness correction guarantees that all points that were different before the lightness correction, remain different.The results of the proposed method are shown for two greyvalue image processing algorithms: 1) sharpening and 2) contrast improvement using gamma manipulation.For these two applications the gamut-limiting process is only advisable when the limiting is applied to the lightness dimension, rather than the chroma dimension.