You mean the way the two cylinders are being colored green is the problem?
Probably as those are the first faces encountered and they are taking on the slicer material. Could set the slicer to use the sliced object material instead, should clear it up as then it won't try applying the slicer green. (I am assuming here the slicer doesn't intersect those two cylinders though it's not 100% clear). Other than that, could add a tiny bit of thickness to the plane ;) Never hurts, e.g. walls and ceilings should always have some thickness anyway.