1. Suppose I have the following in an .xml file:

     <FontString name="Options_ColorLabel" inherits="GameFontNormal" text="Color:">
         <Anchors>
             <Anchor point="TOPLEFT">
                 <Offset>
                     <AbsDimension x="33" y="-225"/>
                 </Offset>
             </Anchor>
         </Anchors>
     </FontString>
    

    I also have a lua function defined in a .lua file that when called with an argument it provides me back a localized string. How do I change the text of this FontString to the localized content?

    I don't think you can automatically using the text attribute. If you want to do it manually you'll need to call, do the translation, and set the text.

    Right. I didn't see a Script element that is available for the FontString. Other Form elements like buttons, check boxes, etc. I was able to do this with a Script OnLoad element. Just wondered if there was a way in the lua that I can reference the FontString and change the text attribute manually.

    You set a script in the frame to which the font string belongs and then access it. That's all, nothing special =)

    I normally construct everything in Lua and then set things explicitly using my localized version.