Automatic white balance in today’s cameras is pretty good and the OM-D is no exception, but this scenario, an image consisting of various shades of green and yellow only, this is the worst case.
In general we tend to make grass much too green, and so do the cameras. Go out and look at it, even on a sunny day in Spring. Try to remember the color. Then go back to Photoshop and shift magenta into your yellows. They need it. Lots of it