Other mistake: Spider-Man is shown web-slinging past several glass buildings, but he does not cast a reflection in any of them. (00:00:10)
The Alien Costume: Part 1 - S1-E8
Other mistake: After tricking police by disguising himself as a policeman, Spider-Man changes his clothes in the middle of traffic with numerous people around but somehow nobody notices this.
Other mistake: Despite being Shield agents the guys shown in the target practice room wear the same uniforms as the guards working for The Kingpin.
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