Visible crew/equipment: After the brief discussion in the hallway outside Linda's office, as Lucifer walks off a green screen is reflected in her glasses. (00:11:50)
Revealing mistake: When Lucifer convinces Ricky not to jump off the building, it is blatantly obvious that the two actors are on a green screen and not an actual rooftop. The green glow around their heads is visible. (00:13:10)
Visible crew/equipment: When Lucifer jokingly says to Ricky that there's "nowhere to go but up", part of the crew/equipment is reflected in Ricky's glasses. (00:15:00)
Continuity mistake: When Malcolm lifts his jacket to show he is unarmed his jacket position changes between the two shots. In the first shot his jacket is hanging low and in the second it's held high. (00:19:40)
Continuity mistake: When Lucifer hands Linda the leaflet in the carpark, the way he holds it changes between angles. In one shot he's holding the sides and in the next he's holding the top. (00:25:40)
Answer: It's Lucifer's blood from when his wings got hit by the bullets. As Lucifer spreads his wings, they're white, and before he wraps them around Chloe, you see a bullet hit his wing above his right shoulder, and the spot turns red. After that, he continues to get shot in the wings before fleeing.
Bishop73
Agreed. His wings take damage and "bleed" similar to how he bleeds when Decker is around.
Ssiscool ★
If they were normal bird's wings, the lower part where there are just feathers should neither bleed like that nor be able to stop bullets, but they are angel's wings, so they behave differently.