Replace Color not working - Photoshop 2018

[ammcjm]

Under Enhance, Adjust Color, Replace Color, I use the eyedropper to select the foreground color ("f9fdff") of my PSD file.  In the Replacement box at the bottom, I click on the Result square to bring up the Color Picker (Result Color) box.  There I type in "ffffff" as the color I want "f9fdff" replaced with and choose OK.  The Result box in the Replace Color dropdown now appropriately shows "ffffff" as the color with which to replace "f9fdff".  I click OK to make the replacement happen and no change occurs. 

Suggestions please!

(Note: Fuzziness is set to 0, I've tried it with Localized Color Clusters checked and uncheck - no success)

[D Fosse]

White, gray or black are not colors. They are the absence of color.

There is no color to replace. The tool works, but it has nothing to work with.

[ammcjm]

Thanks. I was hoping that wasn't the answer but appreciate your reply.

[D Fosse]

Actually Replace Color is a very crude and primitive tool, and I would never recommend it to anyone. Plus it causes a lot of misunderstanding like here. "Color" in everyday language may include white and black, but in Photoshop (and color theory) it has a much more specific meaning, separate from luminance/brightness.

There are much more precise and more flexible ways to do this. Painting on a separate layer set to Color blend mode achieves the same thing, and allows you to use masks to target the area precisely - and reversibly so that you can go back and readjust.

If you need to take an off-white area and turn pure white, you'd use Levels to set the white point, again possibly using masks to target a specific area.

[ammcjm]

Thanks!  I'll have to try that.