In order to avoid collision, theoretically, the color should be 22. 5 degrees, but practice has proved that the four angles of 15, 45, 75 and 90 degrees have good effects. The yellow version has relatively weak visual stimulation and poor visual sensitivity. Therefore, it is generally set as 90 degrees, and the vision is most sensitive to 45 degrees. For example: for the picture of blue sky and white cloud, the green version should be set as 45 degrees, for the picture of dawn, sunset should be set as 45 degrees, a non-45 degrees Angle in magenta and cyan can be set as 15 degrees, black version as 75 degrees.