Database

[{"_id":ObjectId("61ba65af74cf385ee93ad2c7"),"Car_brand":"BMW X7","Plate_number":"8OP66","Model_year":"2018","Company":"BMW","Purchase_year":"2019","Body_color":"red","Mileage":1000,"Price":35000,"Body_type":"crossover"},{"_id":ObjectId("61ba65af74cf385ee93ad2c8"),"Car_brand":"Tesla Model X","Plate_number":"5XR56","Model_year":"2015","Company":"Tesla Motors","Purchase_year":"2019","Body_color":"white","Mileage":800,"Price":25000,"Body_type":"SUV"},{"_id":ObjectId("61ba65af74cf385ee93ad2c9"),"Car_brand":"Tesla Cybertruck","Plate_number":"2ED45","Model_year":"2021","Company":"Tesla Motors","Purchase_year":"2021","Body_color":"gray","Mileage":0,"Price":50000,"Body_type":"pickup"},{"_id":ObjectId("61ba65af74cf385ee93ad2ca"),"Car_brand":"Lamborghini Aventador","Plate_number":"2MN50","Model_year":"2011","Company":"Lamborghini","Purchase_year":"2017","Body_color":"orange","Mileage":700,"Price":45000,"Body_type":"supercar"},{"_id":ObjectId("61ba65af74cf385ee93ad2cb"),"Car_brand":"BMW X7","Plate_number":"3QW14","Model_year":"2018","Company":"BMW","Purchase_year":"2020","Body_color":"black","Mileage":4500,"Price":14000,"Body_type":"crossover"},{"_id":ObjectId("61ba65af74cf385ee93ad2cc"),"Car_brand":"Mercedes-Benz G-Class","Plate_number":"9KI24","Model_year":"2017","Company":"Mercedes-Benz","Purchase_year":"2017","Body_color":"black","Mileage":6000,"Price":13000,"Body_type":"SUV"},{"_id":ObjectId("61ba65af74cf385ee93ad2cd"),"Car_brand":"BMW X6","Plate_number":"2GH47","Model_year":"2008","Company":"BMW","Purchase_year":"2016","Body_color":"white","Mileage":4500,"Price":14500,"Body_type":"SUV"},{"_id":ObjectId("61ba65af74cf385ee93ad2ce"),"Car_brand":"Chevrolet Camaro","Plate_number":"7BV58","Model_year":"2015","Company":"Chevrolet","Purchase_year":"2020","Body_color":"orange","Mileage":4000,"Price":43000,"Body_type":"cabriolet"},{"_id":ObjectId("61ba65af74cf385ee93ad2cf"),"Car_brand":"Ford Mustang","Plate_number":"4AM23","Model_year":"2016","Company":"Ford Motor Company","Purchase_year":"2019","Body_color":"purple","Mileage":2000,"Price":30000,"Body_type":"cabriolet"},{"_id":ObjectId("61ba65af74cf385ee93ad2d0"),"Car_brand":"Dodge Challenger","Plate_number":"6DL73","Model_year":"2020","Company":"Dodge (Chrysler Corporation)","Purchase_year":"2020","Body_color":"red","Mileage":0,"Price":40000,"Body_type":"muscle car"}]

Query

db.collection.aggregate([{"$group":{"_id":"$Body_type","colors_array":{"$addToSet":"$Body_color"}}},{"$project":{"colors_number":{"$size":"$colors_array"}}}])

Result