Chuck is right. Paint ages differently, depending on its original formula, weather, types of service, miles in service, and whether standing in sunlight or shade.
Photos vary, too. And when photos are published, printing inks add still more variations.
A good example is GG-1 4877. NJ Transit painted her Tuscan Red with gold stripes. She looked magnificent! But I'll bet we would have noticed differences if a time warp had put her next to a GG-1 freshly painted Tuscan Red by the Pennsy.
I like Gravely tractors, too. Colors vary from one catalog to another and even in different printings of the same catalog.