This woolen is best called a cloth since it lacks much nap on either side. Olive cloth is often described in the 18th and early 19th centuries. An example from London's Proceedings of the Old Bailey in 1760 a servant was asked to "fetch me a coat from thence, saying, he would find an olive-colour coat there". Green 35/2 linen thread will be the best match for hand sewing. For hand sewing button holes try the nothing matches so the best option would likely be buff buttonhole twist.