The accessory one is always black, but the factory-fit one is interior-coloured. You need to find someone with the same colour interior that also has the luggage net, borrow their VIN and hit the EPC with your stealership
I'm fairly certain they will work. Best bet is to order just one of the hooks and see if it matches (about 70p?), if it does then order the rest
EDIT: I just read that beige is also known as "quartz". So you should ignore my above posting until I can confirm the colour codes!
EDIT2: How about you let me know your car's interior colour code, or in fact the VIN and I can find out exactly what colour the interior is (as far as MB is concerned)