Phone numbers in Walla Walla, WA in 1903

[Phonesrfun]

I live in a relatively small city, Walla Walla, WA which has a current population of about 40k.

A friend of mine runs an historical blog website that features a new group of photos and other such historical stuff each day.  Today his blog features a bunch of ads from the newspaper from 1903.

What I find interesting are the various "prefixes" that seemed to be in place within this town at the time.  Walla Walla was manual until 1956 and later phone books, I.E. 1945 don't make any mention of these prefixes.

The numbers are all 2, 3 and 4 digits long, and are usually preceeded by a prefix, but not always.  Some don't refer to any prefix at all.  Most others have Red, White, Blue, Black, White and Main.

I am wondering if there would have been color coded strips of jacks on the switchboards.  Depending on how many positions there were, the multiples would all have to be coded with the same color.

Here is a link to the ads I am talking about:

http://wallawalladrazanphotos.blogspot.com/2014/03/advertising-miscellany-of-1903.html

My question:  Was this a common practice in 1903 in other towns?

[Phonesrfun]

So, Roger Conklin, a very well respected authority on old phone issues, particularly when it comes to smaller phone companies replied to my question which I also posted in the TCI listserve.  He believes the color designations red, white, blue, and black were for harmonic ringing which was likely in place at that time.  Others have agreed with that opinion too. 

For the benefit of anyone who cares, I did a little research this afternoon.  Here is what I reported in the listserve:

So, today's questions led me to the library where there are city directories.  Here is what I found out:

In 1900 there was a phone company called Inland Telephone and Telegraph Company, located at 7 N. 3rd here in WW, and phone numbers published had the red, white, blue, black and no designations.

In 1902 the name of the phone company had changed to Pacific States Telephone & Telegraph Company located at the same address, with the color designations.
In 1903 the Pacific States Telephone and Telegraph Company relocated to 113 E. Alder where it remained until the early 1930's.  Somewhere in this time frame the color designations were dropped.  I need to go back and see if the actual numbers for various listings changed too.
By 1908 the name changed to Pacific Telephone and Telegraph Company, which stayed the same until it became Pacific Northwest Bell.

My guess from the information Roger has given and from what I think I know of Bell companies would be that Inland had harmonic ringing in place, and was changed over once the new phone company (Pacific States Tel and Tel) moved to its new location.  I am presuming that PST&T was perhaps a Bell Company.  PT&T was for sure.

So, I guess a genealogy of the phone company here is that it was Inland, then Pacific Coast Tel & Tel, then Pacific Tel & Tel, Then Pacific NW Bell, then US West, then Qwest, now Century Link.

Here is a link to a photo of the building that Pacific Tel & Tel occupied until the 1930's when it moved across the street.

http://www.classicrotaryphones.com/forum/index.php?action=dlattach;topic=10456.0;attach=60346;image

This might not be of general interest, but it was fun piecing it together.  Particularly since there is nobody that I know of locally that can tell me directly.