Spider Wars, Chapter 2: Farewell Spider-Man - S5-E13
Revealing mistake: When Spider-Man is web-slinging with Stan Lee, they pass the same group of buildings twice, revealing it to be recycled animation.
Spider Wars, Chapter 2: Farewell Spider-Man - S5-E13
Continuity mistake: When Spider-Carnage has Gwen Stacy hostage, she is bound by portions of his symbiote. When Spider-Man frees her, she is suddenly bound by webbing instead of the symbiote.
Spider Wars, Chapter 2: Farewell Spider-Man - S5-E13
Continuity mistake: When Scarlet Spider is saying that they need to destroy the bomb, you can see one of the arms and tattered costume of the Man-Spider behind him, even though the Beyonder had already teleported Man-Spider to another dimension. It appears to be a shot from Spider-Man and Scarlet Spider's fight with Man-Spider that wasn't used and ended up being repurposed, rather than taking the time to animate a new shot altogether.
Spider Wars, Chapter 2: Farewell Spider-Man - S5-E13
Character mistake: When Stan Lee is asking Spider-Man what he plans to do after saving all of reality, he responds by saying to find the real Mary Jane. Moments later in the final scene, Madame Web tells Spider-Man that she is taking him to find the real Mary Jane, which elicits an incredulous response from Spider-Man, as if he didn't know that was already the plan.
Answer: I believe it was just a way to try and show the suit is "oily" or reflective. It also helps define the character's features since otherwise, he'd just be a flat black color. It's similar to how the black suit Spidey had blue outlines. (I don't know why they chose a pink/red color... maybe because red is associated with power/fire/war, so it's a more "evil" color?)
TedStixon