Recolor a color range of a granulated pattern

Look at the separate RGB and CMYK channels in search of the flattest (most monotone) one. It turns out to be the Magenta channel in the CMYK set.

Make a duplicate of the original file and change its Mode to CMYK. 

Select the Magenta channel and copy it. Do not close the file; it will be used again later.

Return to the RGB version, add a duplicate layer.

Add the Magenta channel as a top layer. Change its Blending Mode to Lumnosity

Merge down to combine the top two layers

Use the Color Sampler tool to mark the image as shown

Jot down the values seen in the bottom Layer, the starter image

Return to the top image and, using Curves, match the starter image values. 

NOTE: When working in RGB, changing tone values can affect color in the image because both tone and color are housed in each channel. Here it affects the darkest shadow values of the image. They shift from neutral toward green. The correction is as follows.)

Return to the CMYK version of the image and choose the K channel It has almost no tone beyond the darkest shadow end of the scale. Copy it.

Paste the K of the CMYK as a layer at the top of the corrected RGB file and change its Blending Mode to Multiply.

Done. Save as a PDF file. View the enlarged illustration. 

At this point you can lighen the entire image if desired.