How much would it be to get a red taxi from Hong Kong International Airport to the JW Marriott Hotel

If taking a taxi, it costs about HKD 290. If you have luggage, it will charge an extra fee, HKD5 per piece of luggage.

Actually, you have a more economical option. In the Airport Ground Transportation Center, you can take the airport shuttle bus E11 and get off at Admiralty Station, Queensway, Which is quite near your hotel. The bus rides is about 70 mins and the bus fare is HKD21.