Several experimental and commemorative paint schemes emerged during the Santa Fe's diesel era. One combination was developed and partially implemented in anticipation of a merger between the parent companies of the Santa Fe and Southern Pacific (SP) railroads in 1984. The red, yellow, and black paint scheme with large yellow block letters on the sides and ends of the units of the proposed Southern Pacific Santa Fe Railroad (SPSF) has come to be somewhat derisively known among railfans as the "Kodachrome" livery, due to the similarity in colors to the boxes containing slide film sold by the Eastman Kodak Company under the same name. Santa Fe units repainted in this scheme were labeled "SF", Southern Pacific units "SP", and some (presumably new) units wore the letters " SPSF". After the ICC's denial of the merger, railfans joked that SPSF really stood for "Shouldn't Paint So Fast."