Color it is viewed, may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive green. The color of an object depends on both the physics of the object in its environment and the characteristics of the perceiving eye and brain. Physically, objects can be said to have the color of the light leaving their surfaces, which normally depends on the spectrum of the incident illumination and the reflectance properties of the surface, as well as potentially on the angles of illumination and viewing. Some objects not only reflect light, but also transmit light
Orange (colour) a symbol of activity. Orange is sometimes used, like red and yellow, as a colour warning of possible danger or calling for caution. A skull against an orange background means a toxic substance or poison. In the colour system devised by the US Department of Homeland Security to measure the threat of terrorist attack, an orange level is second only to a red level. The US Manual on Uniform Traffic Control Devices specifies orange for use in temporary and construction signage. Because of its symbolic meaning as the orange colour of activity, orange is often used as the colour of