Why did Spider-Man colors change?

Answer 1

Well Spider-Man changed color twice;

The original "black suit" was in fact an alien symbiote Spider-Man acquired during the Secret War, organized by the Beonder. The symbiote made him much more powerful, and granted him new many powers (the same Eddy Brock latter acquired as Venom). However, the suit had a mind of its own, and was pushing Spider-Man to commit violent acts. With the help of Reed Richards (Mr Fantastic) Spider- Man got rid of the symbiote, which latter found a new host in Eddy Brock (Venom).

The second time Spider-man donned the "Black suit" was when Kingpin attacked Aunt May to get to Spider-Man. The author gave Spidey a black suit to match the darker mood of the comics. This time, the suit had nothing special, except for the new color.

The other suit Spider-Man wore, was the "Iron Spider" suit given to him by Tony Stark (Iron Man) in gratitude for his support in the Civil War. The suit had many gadgets, including four retractable arms that sprouted from the back and offered Spider-Man more protection. Spider-Man got rid of the suit when he stopped supporting Iron Man's side during the Civil War