Yup, 8x is what you want, but make sure you set the voltage to 1.65V too or you are unlikely to have a stable system.
Your board wont automatically load timings for any speed above 1333MHz which is why it doesnt specifically list support for 1600MHz, but it does say 1866MHz (O.C) so it will support any memory speed up to 1866MHz, you just have to set everything manually.
Weird it would make it red, AMD systems didnt tie the memory controller voltage to the memory voltage like the intel core i series so there isnt a risk to the processor with higher memory voltage and JEDEC states that chips have to be able to withstand 1.975V without taking damage so 1.67 is still well inside the safe range, maybe it just wants to encourage you to stay low.
You can also probably change the clock speed to something higher than 200MHz and then use a lower multiplier; e.g. overclock to 300 and use the 5.33 multiplier. That would give you a memory speed of 1600 so the RAM would be running within spec.
Of course there's no assurance that your system can support this particular level of overclocking.
What you certainly don't want to do is to use that 8x multiplier and then overclock, as the RAM would be operating above 1600MHz and would probably run into problems as memory doesn't overclock well in general.