Translation:The soldier is wearing green pants.
Pants is also singular in English. It stands for "a pair of pants" i.e. one pair. The same is true for "a pair of...scissors/glasses/trousers/jeans etc. However in English the indefinite article is not needed. He is wearing green pants - he is not wearing more than one pair!
Growing up with Dutch family who generally spoke English, we referred to underwear as "broekje" or, as my sister and I called them, "broekies". Now every time I read "broek" in this course, my brain reads "underwear." I was at first a little shocked about this intimate knowledge about the soldier's undergarments :)