You can not add quality, so you will end up with the quality of the lowest image.
You can make it look a little better with contrast, sharping and other tricks.
You're talking about finding images of the very same subject material, shot from the exact same place, and combining them to make an image better than any one of the images you found? I'm not sure I'm following you completely here.
As far as making the colors in two images match in general, have a look at the Image - Adjustments - Match Color function.
You can sample colors by making the INFO panel visible (Window - Info) and hovering the cursor over your images.
I assumed he was talking about a cut and paste from low quality web shot to a higher quality picture, and wind up with the HQ specs.
Thanks for you replys.
I can see that there is some misunderstanding :-)
I think I got the answer: Image - Adjustments - Match Color function.
I do not want to make a low-quality image better. Only adjust, to make them look the same