Why does the color shift when making a selection with color range?

[Allen Birnbach]

I have some color drawings that have been provided to me by a client that were done on white paper.  However, they had to photograph  the drawings using ambient light in conference room so the lighting is uneven.  I decided to use color range, picking the white background and using fuzziness to capture all the paper that might be slightly grey.  When I invert the selection and then try to work with just the colors, adding a new pure white background below that layer, the colors are altered, and the contrast is off as well.  I've having to use hue/saturation adjustments to fix each of the colors, which is rather time consuming Any suggestions of how to make this work better?  I'm working in PS 2022 on a MacBook Pro.

[Bojan Živković]

Try this: after creating selection do not invert selection just create mask. With mask selected in the Layers panel press Ctrl + L to evoke Levels. Start dragging sliders until colors that you want as they are dissapears from view. Confirm and revert mask.

Here is my result:

[D Fosse]

Uneven lighting is best corrected globally, not with selections.

Put a steep Curves layer on top, to exaggerate. Then the correction is easily done with masked adjustments painted in with soft brushes at low opacity.

Delete the top Curves layer when done.