Don,
Here are photos of the various Flyer semaphores that they sold over the years.
The earliest, c. 1916, features a cast iron base and the lower blade features a fish-tale cut. Colors are black base and lower portion of mast, with white mast above.

The cast iron base was short lived, with the stamped steel base appearing by c. 1917. Colors change to dark blue base and lower portion, with white upper mast.

At some point, there is a brown color mast/base

Then there is a gray base/mast version

Not sure if there was ever an early version with the double mast posts that was painted green. The semaphores eventually change to a single mast post, with lithographed blades.

Then a short-lived semaphore blade c. 1935 with the blade being more commonly used on the lighted versions of the semaphores. This one also regressed to having a double post mast. Not sure why, as the ones shown above are shown in earlier catalogs than the version shown below.

Then a different style of mast, which is the latest version

Those are only the double semaphores. The single semaphores are generally similar, but some differences
Again, the earliest one has a cast iron base. Difference between single and doubles is that the single blade semaphore has a single mast post and the top of the post is crudely cut off (ie it is square cut instead of rounded).

This one, c. 1917, features dark blue, and rounded cut on the top of the post, but still has the fish-tale cut to the blade.

Another early one c. 1918, this one without the fish-tale cut to the semaphore

Then a gray base/mast version

Next up is a green mast version. I suspect this one was sold during the same era as the brown mast version of the double semaphore, as I have never observed a brown mast version of the single semaphore.

Then the later versions, again with the lithographed semaphore blades, which apparently are common enough that I did not think to take photos of one.
Again, there was a short lived one with the odd style of semaphore blade, c. 1935

There is also a single bladed version with the late odd-shaped blade, but again, I apparently have not photographed one yet for my on-line photo archive.
The ones with the lithographed blades can come in various color configurations (red or green masts with combinations of red or green bases).
Hope this helps to clarify some of the color/style variations of these.
The rarest of these (based on my experience) are the early c. 1916 versions with the cast iron bases. Specifically the single blade variations, of which I have only observed the lone one in my collection. I am sure there must be more of them, but I just have not observed any others for sale.
NWL