Incident 1: During Gamora's fight with Thanos in Avengers: Infinity War the color of Thanos' blood was purple.
Incident 2: Tony Stark made Thanos bleed. "All of this for a drop o' blood." This time the color of Thanos' blood was red.
Incident 3: Thor shoved stormbreaker into Thanos' chest. This time the color of Thanos' blood was purple.
Why was it red when Thanos was fighting with Tony Stark?