Hi

Does each size, colour need an SKU? Yes each need a SKU. each size and colour is treated like different product. Each size and colour have their own barcode, ASIN and SKU.

Does each variation need to be boxed individually? if you mean when you ship to fba - generally no. but when doing your fba shipment plan it will advise if all variations can be shipped in same box. generally you can put all variations in same packing box because they are all the same type of product just different size, colour.