It is appealing to equate these horses with those mentioned in Revelation 9:7–11 and so conclude that they represent demons. The problem with that equation is that Revelation 9:7–11 are not about horses but about locusts, who look like horses. Instead, the horses of the sixth trumpet appear when the four angels at the borders of heathendom were released from their bondage to invade the land given to the descendants of Abraham.
17 And this is how I saw the horses in my vision and those who rode them: they wore breastplates the color of fire and of sapphire and of sulfur, and the heads of the horses were like lions’ heads, and fire and smoke and sulfur came out of their mouths.