This is my third Katzkin interior (the first was on my Gen1 3s), so I should have remembered that the colors end up being lighter in person against a dark interior, than the samples and squares in the swatch-book (although they are exactly the same colors, it's just a "trick of the eye" depending on the background). BTW this is a 2018 Sport 6 MT.
It looks "saddle" at times, and "pumpkin" at times. (Or maybe that's just a Halloween weekend thing, not sure.) I do like it, though, and I expect that when I add the tint, it will calm down the color.
This is their "premium" or "upgraded" kit, with leather on the faces of seats, headrests and rear armrest, and then they use matching grained synthetic (vinyl basically) on the ends/sides and front seatbacks. I also had them do the door panel inserts, which added $300 to the cost. Ended up costing me $1975 OTD. They remove the original seating fabric/cover completely down to the foam, and then pull the new leather over the foam and fasten it down. Typical 3-year/36,000-mile warranty. In my experience it holds up very well, just don't abuse it, don't leave metal propane tanks on it, don't put sharp stuff in your back pockets and sit on it, clean up spills promptly, etc., etc. To clean it, use a damp clean cloth or diluted Lexol leather cleaner (orange bottle), dry it, and it should be conditioned with Lexol Leather Conditioner (brown bottle), every few months or so.
The Katzkin web site lets you model the options (two-tones in various designs), and you can also do contrasting stitching. Piping is discouraged as it doesn't wear well. My favorite two-tone pattern is "Centers." Mazda has used the "Faces" design in some of their OEM interiors. I prefer something more custom-looking. You can play with the colors more than what the web site suggests. Install takes 2 days, and the installer typically can receive the ordered kit within 2-3 days (depending on geo location and how crazy you go with colors/design). The leather is dyed, not painted.
On Black or White vehicles, I think the Medium Red (a darker red) or Cognac would look fantastic. On Soul Red or Deep Crystal Blue vehicles, I think Camel could be a good color, especially with a Sand interior (double-check it, though, with a swatch). On Machine Gray, if the pictured Mahogany is too bold, step up to Coffee. I think that would look fabulous - should be a little lighter than the brown we see in our top level trims. Coffee would also look great on Soul Red with black interior. Silver vehicles may be ideal for a sporty two-tone Centers design.