You might try the Image - Adjustments - Match Color function.
The other possibility that comes to mind is to set up the Bucket Fill tool with a small but sufficient tolerance, then sample colors from the other image, and bucket-fill them in the target image. This could be facilitated by putting both images up side by side via the Window - Arrange function, then using Alt-click to sample the color, and just click to fill it.
Thank you for the reply. Yes, the Bucket tool is REALLY CHARMING, but it would lose its charm when I say I have over a hundred files to do this. I just simply want to adjust maybe the colors of the second picture to match the colors of the first picture. Is there any way to do this accurately?