LG G5, Samsung Note 4 DE, Note 3, Moto DROID Bionic, DROID RAZR, Galaxy Nexus, Rezound, V9m, VX8000
Verizon, AT&T GoPhone
From what I've seen, solid red is a Facebook notification. Flashing blue is for new email (using the included email app).
There is also red if the battery is low, or if its connected to the charger (you can turn this off in the settings).