What color are runway shoulder markings?

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Runway shoulder markings are indeed yellow. These markings are positioned on the pavement adjacent to the runway to provide visual guidance to pilots and reinforce the runway boundaries. Their yellow color is used to distinguish them from other markings on the airfield and is consistent with international airport marking standards. Such visibility is essential for pilots during takeoff, landing, and taxiing, especially in low visibility conditions or at night. The other options, while representing different types of markings or features on an airfield, do not correspond to runway shoulder markings. For example, white markings typically signify runway or taxiway lines, blue is often associated with taxiway edge lights, and red markings may indicate prohibited or restricted areas.