The red sky was done with Photoshop. Just used the fog editor to make the background white to then use it as a mask, after that, just used a red gradient from top to bottom to give the subtle Hell coloring that's normally seen.

It never occurred to me that the custom Scout cosmetic set is a Madness Combat reference until I saw this artwork. Speaking of the artwork, it's pretty cool! The saturated red works really well with the desaturated gray and white. Was the red sky done in-game with the fog editor or was it done in after-effects?