Hi, the Kirby bag shown above is original. The color originally was dark gray, almost a charcoal color. As the color fades over the years, especially machines not kept out of sunlight, the color changes to lighter gray, yes, sometimes with a pinkish cast and other times with a brown or yellowish tinge. When the bag is in as-new color, it's absolutely stunning. The red and silver logo really stand out in relief against the dark background.
Somewhere along the way, the bag went from solid gray to gray with a silver speckled pattern. I don't know exactly when the change occurred but my guess is gradually as I have seen that bag on machines as early as 518 and as late as the 561, yet I have also seen 518s and 519s still with the earlier plain bag.
And, yes, as far as my Kirbys go, they are all in all-original condition except for the ones awaiting restoration (which now will never happen). I sure wish I had the time to keep them buffed out. Although, now no longer having my workship, having the time to do the work would be a moot issue.......