The "silver titanium" finish on the S10 and S11 Hermes watches looks indistinguishable from the stainless steel in most lighting conditions. In dimmer and more diffuse light, I find that the silver titanium looks slightly darker than the stainless steel. I think this is likely due to the fact that the titanium finish is a coating and you get some destructive interference as some light reflects off the coating and then some reflects off the metal underneath (it's the same effect that creates colors on soap bubbles and oil slicks). To be clear, nobody looking at your watch would ever notice this slightest of differences. Just figured I would mention it.
The matte finish on the Ultra is different in both texture and color tone. I don't have one but I imagine the difference with the stainless steel lugs would be much more pronounced.