As Randy Hees points out in his NGDF post:
The two classes of Tiffany reefers, 26' built in the DSP&P shops in 1880 (12 cars) and 27' cars built by St Charles in 1883 (15 cars) . . . The short 26 foot cars predated the UP acquisition of the South Park, so I see no reason why they couldn't be white, like so many models that have been built. I seem to recall someone quoting early Denver newspaper articles referring to white reefers on the early South Park. Santa Fe reefers of that era where also white.
The 27 foot cars were not built by the UP shops, rather built by St Charles, just after the UP gained control of the South Park. They may have been ordered prior to the UP take over, perhaps after. I can see a case for either color / paint scheme on this latter series of cars, depending on whether the UP exerted any control over the specifications of the order. Prior to the 1885 UP renumbering, freight cars on the South Park and Colorado Central were considered to be cars owned by UP subsidiaries, not yet fully integrated into the UP system as divisions, and were lettered for those roads.
Here is what Randy suggests the Tiffany's looked like under early UP ownership, 1883-1888, if painted UP reefer green:
Color drawing posted by Randy Hess on NGDFI would suspect though, that the green color scheme, if applied to these cars, more likely came along when both classes of cars were repainted with the UP reporting marks in the late 1880's to early 1890's. It would make more sense for the colors to match UP standard practices then.
Just my 2 pennies worth . . .
For more discussion see:
http://c-sng-discussion-forum.41377.n7.nabble.com/Denver-NNGC-Notes-Tiffany-Reefer-Colors-again-UP-Standard-Reefer-Green-td9330.html
Jim Courtney
Poulsbo, WA