It may be that the yellowing is a red herring. I've never seen any difference between the internal parts; the Dark Blue switches that I have look like they should click, but they simply don't. I don't see any grease. Someone pointed out that the sliding collar doesn't strike the shell, but rather is caught by the main slider, and it's that instant that you'd want to damp — which means that putting grease on the slider cam seems like it would not help..
You can see the grease here:
https://geekhack.org/index.php?topic=17221.0
However, you can see that my MX White switch is devoid of grease, and yet it still works as expected:
wiki/File:Cherry_MX_--_click_sliders.jpg
Wodan — I am not sure what I would do with the switches. I don't have any equipment that I could put to use on them. I'd not even manage a better photo than yours (I'd get better focus, but less detail and far worse dynamic range, so not an improvement). I do have one single old MX White switch, but it's still got wires soldered to it and one day I need to see if I can get those off, and without melting the switch in the process (which I've done before).
With Cherry I'm really after documentation.