My Glofish is bloated and losing color. Is it a fatal infection?

The bloating could be infection. It may also be parasitic infection, constipation or swim bladder disease. You cannot discount them being gravid (pregnant). Glo fish are egg layers, so they could be females readying to spawn (release eggs).
First check water chemistry and quality. Clean water is critical to having healthy fish or to having fish recover from illness or injury. Use a home test kit or submit a water sample for testing. Most pet stores will do this for free or for a small fee. An established tank will have 0 ppm ammonia and nitrites with a nitrate level of 20 ppm or less. If your tank shows any level of ammonia or nitrites, perform a partial water change (no more than 30% total volume at a time) using conditioned water. Makebsurebit is temperature matched as well to prevent stress or shock. Glofish do best between 72 F and 80 F.
Once water quality is squared away, fast the fish for 2-3 days, then feed tiny bits of cooked and shelled green peas. This will help with constipation and bloating. Feed peas until they are swimming normally and the bloating is resolved. If the peas don't help, try broad spectrum antibiotic, such as erythromycin or ampicillin. You can find either in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated. An "all in one" product, such as Lifeguard (by Tetra) can also be used. This will treat multiple types of infection with one medication.