How do I update a record containing a Multiselect pick list with multiple values?

Hey API'ers,
I need some help in setting multiple values in a pick list through the API.

As an example, I have a contact record, and one of the fields is the Multiselect pick list Favorite Color.
Normally if John Doe just liked silver I'd update it like so
<FL val="Favorite Color">Silver</FL>

But what if he likes both Silver, and Blue?

I'm going to take a wild guess that it's either this way

<FL val="Favorite Color">Silver</FL>

Or some subset of this
http://www.w3.org/2005/07/xml-schema-patterns.html#Enumerated

But I'm not sure, and I cannot find this in the documentation. Thank you for your help.