How do colors on old photos change? How can I correct the color shift using Photoshop?

you select the area and apply a color map using (Levels, Variations, ... etc), to select the color Hue itself you need a reference, experience or artistic sense.

Play with adjustments. IMAGE > Adjustments, with that you can find whatever you want to achieve in your image.

Select the area of colour first then go to then press Ctrl + U or go to Image / Adjustment / Hue/Saturation and choose the colour whatever you want. 

 

You are welcome 

 

Wajid 

 

There are many ways to do color management in Photo shop but the easiest way to do this is to use the Replace Color Tool.

Select Image > Adjustments > Replace Color .

This tool must be applied as an adjustment and cannot be used as an adjustment layer so apply it to a duplicate of the background layer .

With this tool you click on an area in the image that you want to change the color of . Click the add to sample eyerdropper and then click to select more of the color to change .

You will need to click on all the colors in the image that represent the color that you need to alter . You can test the result by dragging on the Hue slider at the bottom of the dialog to see if the selection is accurate and that the color change is effecting the area you want to effect.

 

In photoshop there are several ways to change the colours even can change the selective colour also. From brush with proper adjustment of pressure, tone and transparency u could find the result u want also. You can play with channels, selection, history, filters etc.

I am not a photographer but what I know is that colours change by light, oils "from our hands" and humidity.