The red text doesn't actually exist yet as pixels! What you are seeing is the GIMP path created when you select "Text to Path." To make the text appear, click on an image layer (not the layer with your text box). Then go to the Paths panel and click on the path named after your text. Then select Edit | Stroke Path or hit the swirly+paintbrush at the bottom of the Paths panel. Pick how heavy you want your text and press "Stroke" to render the pixels of your text-on-path.
Example: After text-to-path, I see this:
Note the red "foo bar bat," just like you are seeing. I go to Layers and select the Background, which is an image layer:
I then go to Paths, select the path, and hit Stroke:
Per your followup question, the easiest way I know of to fill the text is to right-click on the text path in the Paths panel and choose "Path to Selection" (or hit the red square fifth from left at the bottom of the Paths panel). That will select the interior of your letters. You can then select one of the Fill options from the Edit menu. For example, after a fill with foreground color:
(note that the selection marching ants are visible in this screenshot).
Remember to pick the order (stroke then fill, or fill then stroke) based on the effect you want. The fill will overwrite the inner half of the stroke since the stroke is centered on the path.