I was testing a new armor when I noticed a glaring difference in the skin color:
http://www.imagedum.com/images/563_problem.jpg

You can see the difference in one blink: the face is a bit pale while the body is vibrant and bright, and the two obviously doesn't share the same color

Is there a difference in the way Oblivion handle face and body skin texture? I know the body is part of the armor so it might have something to do with normal map, but really, the difference is just too great.

Is there something that I can do about this?

Well I use this ... http://www.tesnexus.com/downloads/file.php?id=18669 ... But sometimes those things you just have to ignore unfortunately. I've never been able to get it exactly perfect. Close but still ... that's when I turn to the link.

The main problem is that the face texture is combined with all those adjustments to age, beard, eyes, brows, etc. and the result baked together to produce the one that gets used in-game. If any of those adjustments bleed to the edge of the neck, you get a seam, and the overall tone of the face can get out of step, even if the edge doesn't. The color adjustment that is also applied to the body textures is just part of that, and I suspect the addition of all those changes doesn't always work perfectly.

Body = base texture + race modification + tone sliders
Face = base texture + race modification + tone sliders + eyes, beard and other sliders.

The things is that "+" is quite a complex operator when it comes to textures, and the math is a bit suspect in chargen.

Extreme values seem to work well, e.g. a completely black Dark Elf or a very pale Nord, but the intermediate shades are tricky, and a good neck seam often means a blotchy face.

Given the way the Oblivion clothes fit, though, you can put it all down as tan lines!