I think the Colts are a solid, well-coached team with a quality defense. But the Ravens, with Lamar Jackson, trump them especially in this spot. 
Baltimore is fighting mad after outplaying but losing at home to the Steelers last week because of four turnovers. The Ravens' defense is better than it was last season and their offense has more firepower than the Colts. Baltimore is off its best running game of the season - and it came against the very tough Steelers. 
Indy hasn't faced the competition Baltimore has. The Colts have feasted on the Jaguars, Vikings, Jets, Bengals and Lions. They lost to the Jaguars and struggled against some of those other lower-echelon teams. The Colts haven't gone against a QB who is the dual threat Jackson is. They also haven't encountered such a strong running attack. 
The Ravens have done their best work on the road winning nine straight away games.