"Extending" dark Vulpine fur for legs?

[giantsnickersbar]

Hello, I'm trying to replicate the gradually darkening fur on the Vulpines' hands-to-elbows for feet-to-knees. Right now, the "dark part" truncates right above the ankle, and I'm trying to figure out how to extend said "dark part" to below the knee, as seen in https://www.nexusmods.com/skyrim/mods/79390 

 

I'm a total noob to programs like GIMP or paint.net, and the textures don't seem to give me the best visual cues for where to begin even editing. Below are the textures I use for reference - I'm really not sure where to start. 

 

I'd greatly appreciate any help from anyone what/whosoever.

 

Thanks! 

VulpineMaleBody_d.dds VulpineBody_d.dds