The warm and cool versions started with Kodak E100G. Another version of this film existed, called E100GX and it was essentially just a warmer version of the same film. In making that version of E100G, we quickly realized how useful this was and even noticed that some other film scans benefit from a slight warming in some situations. So, soon all the films had it. What we also found is that slide film is prone to turning a bit cool in shadowy areas or in early evening sort of light, and it can be a very nice effect. Thus cool versions of all the films were made. These cool versions also tend to be useful at night, in situations where the scene is lit by warm tungsten lighting. While white balance can tune the overall color temperature, the warm and cool versions make their changes in different ways that are often complementary with white balance adjustments.
Be sure to watch this great walkthrough video on VSCO Film 04 here: http://vsco.co/blog/vsco-film-04-walkthrough-video.
As always, contact us at firstname.lastname@example.org if you have any additional questions.