Route Marker

Route Markers are the flags that mark the places where teams must go. Most Route Markers are attached to Clue Boxes that contain clue envelopes, but some may mark the place where the teams must go in order to complete tasks. The colors of yellow and red signify the The Amazing Race and are used on arrows, banners, and other signs for the racing teams.

Exceptions
Route Markers are always colored yellow and red, with the following exceptions:
 * The original Route Markers used in Season 1 were colored yellow and white. The current colors (with red added) were adopted in subsequent seasons so that the teams would have an easier time spotting them.
 * During Season 3, the production visited Vietnam; while there, the flags used were a solid yellow, to avoid confusion with the former flag of South Vietnam,(CBS.com) which differs from the current flag of Vietnam. The flag of the former South Vietnam is used as the "official" flag of some expatriate Vietnamese communities in the United States,Vietnamese activists push for old flag and is something of a holdover from the Vietnam War. It is a potentially politically volatile subject, and the producers avoided unintended comparison by using the solid yellow color scheme with no red striping. In Season 10 when the show visited Vietnam, the flags were yellow and white.
 * Season 8's Route Markers were colored yellow, white, and black.