traditional color of warning and danger, and is therefore often used on flags. In the Middle Ages up through the French Revolution, a red flag shown in warfare indicated the intent to take no prisoners. Similarly, a red flag hoisted by a pirate ship meant no mercy would be shown to their target. In Britain, in the early days of motoring, motor cars had to follow a man with a red flag who would warn horse-drawn vehicles, before the Locomotives on Highways Act 1896 abolished this law. In automobile races, the red flag is raised if there is danger to the drivers. In international football, a player who has made a serious violation of the rules is shown a red penalty card and ejected from the game. Several studies have indicated that red carries the strongest reaction of all the colors, with the level of reaction decreasing gradually with the colors orange, yellow, and white, respectively. For this reason, red is generally used as the highest level of warning, such as threat level of terrorist attack in the United States. In fact, teachers at a primary school in the UK have been told not to mark children's work in red ink because it encourages a "negative approach". Red is the international color of stop signs and stop lights on highways and intersections. It was standardized as the international color at the Vienna Convention on Road Signs and Signals of 1968. It was chosen partly because red is the brightest color in daytime (next to orange), though it is less visible at twilight, when green is the most visible color. Red also stands out more clearly against a cool natural backdrop of blue sky, green trees or gray buildings. But it was mostly chosen as the color for stoplights and stop signs because of its universal association with danger and warning. The 1968 Vienna Convention on Road Signs and Signals of 1968 uses red color also for the margin of danger warning sign, give way signs and prohibitory signs, following the previous German-type signage (established by Verordnung über Warnungstafeln für den Kraftfahrzeugverkehr in 1927). The color that attracts attention Red is the color that most attracts attention. Surveys show it is the color most frequently associated with visibility, proximity, and extroverts. It is also the color most associated with dynamism and activity. Red is used in modern fashion much as it