I have been away for a couple weeks and so this is late getting to you.
The 25th Kentucky, as vanguard of Cruft's Brigade, did indeed fire into the backs of an Illinois regiments but I have sources that state this was the 11th Illinois. This regiment had been holding the crossroads of Wynn's Ferry Road and the road to Bufford Hollow when it got the friendly fire. They were then hit on two sides by the 2nd Kentucky Infantry (CSA) and Forrest's 3rd Tennessee Cavalry and they crumbled. 63 me died at that crossroads and they are the first graves at the Ft. Donelson National Cemetery.
I will have to see if any of my sources have anything for the uniforms of the 8th Illinois and get back to you. I will also check to make sure the unit getting this friendly fire was the 11th.