Ted, that color photo doesn't seem to show that very light gray, as shown in the OP's photos of his #2626. Now the smokebox color is certainly more "grayish", however.
The Lionel NP 2626 does use a very light grey. It is definitely a much lighter shade than the NP used for boiler and cylinder jackets. But then the Lionel locomotive isn't a scale model. It is one of the last new toy or traditional O gauge locomotives to come from Lionel before the world of O changed with the advent of the MTH scale Challenger in 1994.
Since then we have had several NP scale steam locomotives come to market. MTH has offered G-1 0-8-0 switchers and Z-6 Challengers. Sunset/3rd rail has done A-3, A-4 and A-5 Northerns, Z-5 Yellowstone and Z-6 and Z-8 Challengers and the Timken models are on the water now.
With their Y-3/USRA 2-8-8-2 tooling MTH could do a Z-4. The MTH USRA Heavy Pacific could also be used for a reasonable approximation of a Q-5 or Q-6 Pacific.
BTW, The photo of Four Aces on the cover of the Mainstreeter was taken as it entered the City of Tacoma watershed on its last day of operation on August 4th, 1957. NP 2626 pulled a passenger special from Seattle to Cle Elum and return. The more recent steam excursions over Stampede Pass use the new mainline that was relocated in 1959 for the construction of Howard Hanson Dam. If you were looking down at the right moment you could see the location of the 1957 photo below you. The silver painted truss bridge carries the Tacoma Water pipelines across the Green River and the and the bridge and buildings are still there.
