Can I set a text field to use RGB?
Yes.
After you have set the text field, use the "Field Scripting" tab to select the HTML Markup option. Then use the "Insert Code Snippet" menu to insert the Font tag. Paste the RGB hex value into its color="" tag.
For example, while RGB black values are R 0, G 0, B 0, it's corresponding hex value is #000000 (Photoshop, etc. and online RGB to Hex converters will provide the value for a specific RGB value).
The resulting HTML script will look like <font color="#000000"></font> (for this example, the face="" fontsize="" can be deleted.)
Now place your cursor between the two font tags, and use the "Fields" menu to insert the field you are adjusting. In this example, the Name field is the one we are setting to RGB.
The end result will look like this: <font color="#000000">Name</font>
Save, Commit changes, Test.