I first thought, yes, a typical Chip question. However with a slide being the final product, a lens can have some influence.
A hue can easily be filtered out in a neg/pos process, for slides one would have to use a CC filter at taking.
However when looking at a slide in ambient lighting, room and projector lighting are of effect too.
Low saturation of a lens would affect both neg.pos process as a slide.
The two issues you brought up, dials and left or right focusing, are even more reasonable questions.