I had the exact same problem once. I had to tinker with the TextureParameters (HAIR_Mask, HAIR_Diff, HED_Mask and HED_Diff). I can't remember exactly what I did, but I think I either re-uploaded the modded files, or I reset them all to default textures and then re-added the modded textures again.
Here's some of the default files. I suggest just overwriting your modded textures with these defaults until you figure out which parameter is the one causing the green stuff:
HAIR_Mask: biog_hmf_hir_pro.Hair_PonyTail.HMF_HIR_Ptl_Diff
HAIR_Diff: biog_hmf_hir_pro.Hair_PonyTail.HMF_HIR_Ptl_Diff
HED_Mask: BIOG_HMM_HED_PROMorph.Masks.HED_PRO_Mask3
HED_Diff: BIOG_HMF_HED_PROMorph_R.Diffuse.HMF_HED_PROCustom_Frek_Diff
If that doesn't help... it has something to do with the TextureParameter values. :c That's all I know, unfortunately. If it's possible the wrong texture got replaced, you can open an old vanilla save of your character and make sure ALL of the TextureParameter values are the same except for the modded ones (which should just be HAIR_ and HED_, as far as I know.)