Titanium is stable in the air at room temperature and only produces "colorful" changes when heated at high temperatures for a period of time.This is mainly because when titanium metal is heated in the air, it will react with oxygen to form a dense oxide film. This oxide film can not only protect the surface of titanium metal, but also cause the color change of titanium.
The reaction equation for titanium oxidation is Ti+O2==TiO2, the reaction condition is high temperature heating. When the temperature is low, the oxide film on the titanium surface is almost transparent, which is difficult to be noticed by the naked eye, but as the temperature rises, the oxide film is slowly thickened and interferes with the light, making it appear a different colour to the human eye. So the thickness of the oxide film determines the color of the titanium surface.
According to relevant studies, after being heated in air for half an hour, the surface of titanium heated at 200℃ is silver white, 300℃ is light yellow, 400℃ is golden yellow, 500℃ is blue, 600℃ is purple, 700℃ - 800℃ is gray-red, 900℃ is gray.