When using pH test paper/indicator sticks you should also: 1  Make sure to only use paper/sticks that have not been previously wetted. 2  Wait for the color to stop changing (1-2 minutes maximum) before matching the paper/stick to the color key.
Red and White Regulatory Signs. Red and white regulatory signs tell you about regulations you must follow. For example, the DO NOT ENTER sign tells you there is danger ahead because vehicles will be coming toward you, usually on a freeway off-ramp or one-way street. The WRONG WAY sign may accompany the DO NOT ENTER sign.
What are the colors of the warning signs that indicate hazards ahead, such as curves in the road or narrow bridges Black letters or symbols on a white background. Black letters or symbols on a yellow background. White letters or symbols on a blue background. White letters or symbols on a green background.