Database
[{"_id":ObjectId("5e6ffe413f71835ae3aa4b60"),"f":"Paul","id":11811,"l":"Green","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b61"),"f":"John","id":11811,"l":"Green1","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b62"),"f":"jess","id":11811,"l":"alba","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b63"),"f":"jessica","id":11811,"l":"Greene","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b64"),"f":"johnny","id":11811,"l":"Greèn","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b65"),"f":"Paul","id":11811,"l":"walker","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b66"),"f":"johnny","id":11811,"l":"Green","r":64},{"_id":ObjectId("5e6ffe413f71835ae3aa4b67"),"f":"johnny","id":11811,"l":"GREEN","r":64}]
Query
db.collection.aggregate([{$addFields:{result:{$or:[{$regexMatch:{input:"Paul Green",regex:"$f",options:"i"}},{$regexMatch:{input:"Paul Green",regex:"$l",options:"i"}}]}}},{$match:{result:true}},{$project:{"result":0}}])