why is it that when I duplicate a game object with text mesh pro and I adjust the color of the front it adjust that color for both components?
Because the color settings are shared. You need to create a separate color settings for different TMP objects if you want them to look different.
The Vertex Color is unique per text object as it is part of the geometry of the text object.
Properties such as Face Color, Outline Color, etc. are Material properties and as such will apply to all text object that share the same material.
In order to define and use different visual styles on a text object, you should be using Material Presets which are explained in this video.
There is a naming convention that must be followed when creating material presets and for them to be listed in the Material Preset pulldown menu of the text object. A search on the Material Preset topic should reveal many additional posts.