Variety is the spice of life.
Does it matter if all the tenders are lettered in the same style? I could see lettering some of them in alternate styles. When logos changed, they did not change overnight, it took some time and old logos showed up for years after the official change. So far as the micro-interpretation of locomotives goes, you can have different eras interpreted on the property simultaneously, just so long as you don't try to interpret that logo "X" coexisted with building "Y" if the logo had disappeared long before the building was constructed.
In other words, you can paint a tender with a flying Grande and say "This is how the D&RGW painted their locomotives & tenders" but you could not then park that locomotive in front of the Antonito depot and say "This is exactly what the Rio Grande did" if you included the building in the interpretation.
Clear as mud?
Dave