I blotted out the palm area on and alpha png for you. If the look you are using has a custom specular texture you can unpack the var it comes from and add this to a new layer in photoshop or gimp to darken just the palms and export a new texture and put it in the limbs specular slot in vam. (you might need to tweek the layer opacity to get the effect you want.)
It may only work for Base female uv layouts though, if it doesn't line up with the palms on your texture set you'l have to edit it manually.
If the look doesn't show a custom specular map in textures, then there are some built in ones you can use in custom>atom>person>textures>femalebase>limbsS.jpg
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