They were? I've never seen any photos or read any text that said they came in dark green. I thought the only dark color the Bi-polars wore was the early Black.
This is correct, no Bipolar ever wore green. Only black, orange/maroon (ft. silver, sometimes), and finally yellow/grey.
"For the first 30 years, the Bipolars' paint scheme remained basic black. Occasionally, they were given white trim, but no colors were applied until after the arrival of the streamlined Olympian Hiwatha. Like other Hiawathas of the 1940s, the Olympian's cars were orange with a broad maroon band at window level. Diesels and steam engines used for pulling Hiawatha trains in the Midwest were painted maroon and orange to complement their trains, but no standard pattern existed. In 1948, [Bipolar] E1 was given orange ends, silver stripes, maroon side bands, and a dark gray top. It was a paint job inspired by the pattern of the Fairbanks-Morse diesel sets assigned to the Olympian Hiawatha. In 1949, [Bipolar] E3 was painted in a different Hiawatha pattern. This one had a maroon band around the locomotive and silver wings on the nose. It resembled the Fairbanks-Morse diesel sets that had chrome plated wings on their fronts.
"E3 was the Bipolar displayed at the 1949 Chicago Railroad Fair. After its return, the silver wings pattern became standard for all but E1. This remained so until 1952, when a pattern identical to the one used on Little Joes and 1950 era diesels was adopted.
"The Deer Lodge shops repainted [the Bipolars] in mid-1958 to conform with the Milwaukee's new, Union Pacific inspired, yellow and gray passenger paint scheme. The railroad adopted these colors after acquiring the contract to haul Union Pacific streamliners between Omaha and Chicago. It was proud to provide this service, and thus adopted the UP colors system-wide for its own passenger trains."
src: Noel T. Holley,
The Milwaukee Electrics (1999)
The Bipolars also went through a number of visible changes for those first 30 years - with changes to the sandboxes, cooling coils, boiler room doors, air compressor piping, hot air vent stacks, and numberboards. They also used high pitched steam whistles until the 1930s until they received air horns. My favourite detail is that their headlights were replaced with new sealed-beam headlights in the late 1940s, but some Bipolars got 3 bulbs, and others got 4. Which numbers got which? Who knows! Bipolars are fun.
Cheers,
SM