Photoshop replace color turning gray

Quick answer：

In Photoshop, when you use the 'Replace Color' tool and the colors turn gray, it typically indicates that the tool is not detecting enough color information. This can be due to a low color range or lack of contrast in the image. To fix this, you can adjust the Fuzziness slider to increase the range of colors that will be replaced, or change the color range to match the specific colors in your image.