When applying a LEVELS ADJUSTMENT, you can set black and white points in order to lower the color tints. You might think to yourself, “Where are the darkest and brightest spots in the image?” Go to New Adjustment Layer / Threshold and you will find those areas. It can also be accessed through the LAYER dropdown menu.

Next, adjust the slider position to the right until a few white spots remain in the document. Use the COLOR SAMPLER TOOL and define a point. Adjust the slider to the left until a few black spots remain, and define a second point.

One could also find a neutral gray in the image by using a THRESHOLD ADJUSTMENT LAYER. Add a new blank layer between the original image and the THRESHOLD ADJUSTMENT LAYER, and fill this layer with 50% gray. Go to Edit / Fill, then select 50% GRAY under CONTENTS and click OK.

Change the blending mode of this layer to DIFFERENCE. Select the THRESHOLD ADJUSTMENT LAYER again and move the slider all the way to the left. Slowly move the slider back to the right until black dots start to appear. These are the neutral gray areas in the image (if neutral grays are present). Add a COLORSAMPLER SPOT

Now delete both the threshold adjustment layer and the 50% gray layer. Create a new adjustment layer, LEVELS. Use the first Eyedropper tool to click on the darkest area, then use the third Eyedropper on the brightest area.

Now you can use the gray Eyedropper tool on the third Color Sampler spot. The color tint will be decreased. Color Sampler spots can be deleted by dragging them off the canvas with the Color Sampler tool.