This was the article i mentioned in our offline discussion:
Learn how to get the most out of the new Kodak E100 Ektachrome slide film. See examples and find out the best way to expose this film.
www.alexburkephoto.com
Seems that Alex had similar problems with the colors of E100 first.
But it was a Tiffen 812 filter

The 81B works great with Provia 100F to get its cooler rendition warmer, while the 812 knocks down the E100 greens a bit with the slight magenta of the filter, but not so strong as to
get into the Fuji-realm. Needless to say, i was photographically socialised on Velvia, so i kinda like the magenta
@etn: I will order the filter soon, there are 2 rolls of E100 left in my freezer and if i like it with the 812, maybe i will use it more often.
On-Topic:
I am also going to do photography in the autumn, the first trees are changing their color already.
My primary films are the Fuji slides. I would also recommend Velvia 50, but be careful with the issue of effective speed, check or test in advance with your lab.
Provia 100F + 81B(optionally) is also a combination that performs well. Maybe easier to start with than Velvia and the speed is 100ISO in every lab.
Here you can see some of my photographs to get a feeling:
17 Followers, 2 Following, 79 Posts - See Instagram photos and videos from Photomultiplier (@prismatic.light.photography)
www.instagram.com
Mostly Velvia 50 but also Provia 100 and a bit of the mentioned Ektar.
Details are in the description.