Look at the Options Bar, and set the sample size to 5 x 5. This will give you a good average color from a sample size larger than just one individual pixel.
Hold the Shift key, and you'll see that the cursor changes. This signifies that you're ready to lay down a Color Sampler. Find a good spot to sample the color you want, and click there. You may lay down up to 4 Color Samplers in each image.
Look at your Info Palette and you'll see that it has expanded to now include a pane (or panes) that display(s) the color component make-up of the spot (or spots) where you dropped a Color Sampler (or Samplers). In that pane you'll see a tiny little eyedropper icon, right below the "#1". Click and hold for a drop-down menu. Change the read-out to CMYK. This won't change the color-mode of your image, so don't worry about that. It just makes the following steps more intuitive.
Write down the values for C, M, Y, and K.
Open the second image in which you want to match the color to a similar color in the first.
Now, for one of the most important parts of the process:
Make an accurate selection of the areas you want to adjust. Save it as an Alpha Channel (Select---»Save Selection...New Channel) just to be on the safe side, and save your changes to the document.
Using the Eyedropper again, Shift-Click to drop a Color Sampler in the new image, in an area that is similar in brightness as the sampler in Image 1.
Change the readout of this new sampler to CMYK.
With your object still selected, go to "Image---»Adjustments---»Selective Color..."
Choose a color in the drop-down menu that is as close as possible to the color of the area you want to adjust.
Now, while you keep an eye on the Color Sampler pane in the Info Palette, adjust the sliders in the Selective Color dialogue. You'll see the numbers change in the Info Palette. The numbers to the left of the slashes (/) are the "before" readouts, the numbers to the right of the slashes are the "After" readouts.
Play around adjusting these Selective Color sliders until the "After" numbers for the second image Color Sampler match (or get really close to) the C, M, Y and K values you wrote down for the Color Sampler in the first image.
Sometimes you'll need to work the sliders for more than one of the Selective Color drop-down menu colors. I usually start with the drop-down choice of "Neutrals," because it often allows me to do most of the correction there...lots of bang-for-the-buck. Also, you may need to make Selective Color adjustments, hit "OK" and then call the Selective Color dialogue up a secondperhaps even a thirdtime.
Just match the "After" numbers for Image 2 to the Before numbers that you wrote down for Image 1.
There are other methods for doing this, but this is one of the easiest ways.
Keep in mind that the changes you make are destructive (i.e.: not reversible after you save and close the document). Because I trust my abilities, I know what I can get away with, and I'm usually satisfied with the results. If you have any worries about making permanent changes, just duplicate the layer you want to work on so you can go back to the original color if you need to.
When you're finished, you remove the Color Samplers by again selecting the Eyedropper tool and (Shift+Option) [Shift+ALT] clicking (see the scissors cursor?) on the Color Sampler icon (s) in the image window.