hi Floor
i may have mentioned an inaccurate or "ballpark" date- sorry!

the tassel or "liberty" necklace style is all around in that Edwardian period.
there is plenty of evidence of women on Suffragette demonstrations in London wearing green white and violet- garments as well as jewellery, but i cant locate the references at the moment, though i researched this some time ago and worked with a journalist who documented a lot of suffragette jewellery of that time done in enamels using green, white and violet, also commemorative medals, plaques, etc. One of the artists was Ernestine Mills who lived near Holland Park in London, and was taught by ?Edwin Fisher i think.
There are reports of window displays at the department store "Liberty's" in London of jewellery in Suffragette colours.

i suspect Susan Dods was just guessing. Maybe in USA they used other colours?