This group is the most difficult to categorize. Women who fall into this category choose their clothes for their simplicity, classic style and modesty. They seek to express their religious convictions through what they wear. Skirts and jumpers are popular, but trousers for women tend to be perfectly acceptable. Least likely of my religiously observant dress designations to choose to cover. Women in this group are most likely to have shorter hair styles, as shorter can be simple and easy to care for. Makeup is often avoided as a statement on simplicity, but jewelry is common, particularly earrings. Actual plainness (solid colors, simple print, limited-palette wardrobes) is a hallmark of the plain modern look. There are neither anachronisms nor symbolically or traditionally important items.
Some plain modern resources:
AND now Friends, so many Monthly Men's Meetings as you have in your County, you may have so many Monthly Women's Meetings; and if once a year, at least, you had a General Women's Meeting; it would be well (for in some Counties they have as many Quarterly Women's Meetings as Mens) and in others they have only two in the Summer-time, because the Ways are foul and Days short in Winter. . . .
. . . And that all Friends, who are not already provided, nay speedily procure convenient ...
I am not Amish or Mennonite, but some people who come to my website are interested in knowing more about these groups. I can recommend these books as authoritative and relatively inexpensive sources of further information.