Changing color of individual words with a background in MOGRT template

Unfortunately, there is no way to retrieve a specific word from a text string and change the color of only that word. You would need to work out a track matte and size adjustment for a fill layer if you were going to highlight just one word in a line. The workflow is complicated by multiple lines. Adding a Point Control that changes the position of a shape layer that is defined by the sourceRectAtTime() value for the text layer along with a height and width Slider control to resize the track matte layer would make it doable. 

Another option would be to use multiple text layers for each word and work out a multi-line alignment expression, but that would be a pain to edit and create a huge graphics UI in Premiere Pro. 

You can select the comp with the background layer, use the Extended Graphics Panel to solo all properties, then just grab the background opacity for the background layer and drag it to the EGP and give it a good name. 

That gives me another idea. You could use two Point Controls to change the size and position of a shape layer background that uses the text as a Track Matte to position your highlight over any of the words in the text field. That's probably the way I would handle it. An expression for size generated by the point controls, and an expression for Shape Layer position based on the actual position, left, and top values for the text layer derived by sourceRectAtTime. That would probably present the Premiere Pro user with the easiest interface.