Hi Georgie and welcome again.
In the original livery lower sides, frame and bogies were
grey.
At some point that, assuming from photos, I think it was 1988-89, grey color was replaced by
pale/light blue in a different than the main color shade.
It seems that by 1990 (changing point between eras IV/V) not all locos have been repainted and I don't know if and when that happened for all of them.
So, probably, Fuggerth correctly categorized both of them to era IV/V.
About the MTB 254 livery, you better ask erail
I hope I have answered most of your questions
Panagiotis