When Cambridge Seven developed the color coding identity for the MBTA in the mid-1960s, the original plan was for all equipment on all modes to be painted in a standard gray and white scheme with yellow doors. Prior to the Cambridge Seven plan, surface line equipment (bus, streetcar, and trackless) were painted in the tangerine and cream paint scheme, Blue Line cars were in a two-tone gray with orange stripe, Orange Line cars were painted in a dull orange and gray scheme, while the 1963 Red Line cars, which were funded by money from the state, were painted in "state colors" of blue, white, and gold.
A lot of buses were delivered or repainted in the gray scheme, a large number of Green Line PCC cars where repainted, three-pairs of Orange Line cars were repainted, and one trackless trolley, It was found however that the "Gray Ghost" scheme did not hide dirt well and was hard to see in some weather conditions. The 1969 Red Line cars were delivered with unpainted brushed aluminum and a thin red stripe. By 1970 , they had stopped repainting PCCs gray, and a couple of gray ones were actually repainted back to orange. In 1971, it was decided that rail cars would be repainted or new ones delivered in the color of the lines they were operating on and buses would be painted yellow. That has held, for the most part, since.