I am one of these guys which switched from narrow-bandwidth red, green and blue LEDs to white-light LEDs. Initially, I thought that I can optimize the color separation between the different color channels by a careful selection of the LEDs wavelength. I even tried to calculate these optimal wavelengths - only to figure out that the result was sub-optimal.
The reason for this is probably that the filter curves of the film’s magenta, cyan and yellow are unknown (at least to me). So you might end up with sampling narrow bands of wavelengths were the dyes have some dip in their response.
I tend to align myself more with Pablo’s (@PM490) approach - using a white-light LED with a mostly flat response. Specifically, I am using some Osram LEDs. In this way, you kind of averaging over possible dips in the dye’s response better.
The actual color temperature is probably not that important, for several reasons (but I am still looking into that by myself - so the following is only preliminary). I compared the results using the HQ camera with the normal color science and a color science specifically optimized for the Osram LEDs I am using - the results were visually indistinguishable (I will have to redo this, not sure any longer whether I made a mistake here). Provided, the correct white balance had been applied.
More importantly, in my experience, the film characteristic can change from roll to roll. I have footage from several rolls of Kodachrome from a 1981 San Francisco trip - were one roll features a funny greenish tint. One can correct in the post, but of course the colors will be anything than correct.
Furthermore, S8-film stock only knew two color temperatures: daylight and tungsten. If you were recording with different light (say fluorescent ones), you’d end up with quite some color casts. Again, potentially you can correct this in post production.
Also, once you start scanning different brands of film, you will notice color differences between the different film stocks. Kodachrome is quite different from Agfachrome, for example.
Ideally, you would have for each type of film a color chart target to adjust the colors in a perfect way. However, it is close to impossible to obtain such a thing for old film stock. Also, I think today, you would color grade the original scan anyway, to meet current audience expectations. So the final look will be anything than true to the original color anyway…