Sounds like Springtails, but their color is typically cream to reddish brown. I have never seen a green one. They are not considered a pest in a compost or Vermicompost system, but can be a pest in your garden or potted plants. To avoid transplanting them to your garden or plants, spread your Vermicompost out on paper in a shaded, dry area until the moisture content is below 25%...

To help control either Springtails or mites in your GWF (I am guessing the moisture content in your bins may be a bit too high) try adding some shredded newspaper to your mix and keep the moisture content around 65%. My favorite control method is to put a 1" layer of fluffed hair (from the vacuum cleaner if you have pets, or from the local barber shop) with a couple of light puffs of DIATOMACEOUS EARTH on it. DE is not an insecticide, and is commonly used for feed and grain storage to protect against insect damage, and around the home for ant and spider control.