Which of the following is not a prohibited color for wind direction streamers on the goal posts?

When considering the use of wind direction streamers on goal posts, the NFHS rules specify certain colors that are prohibited due to various reasons, including visibility and signaling clarity. Among the provided choices, blue is not included in the list of prohibited colors.

This means that blue can be safely used for wind streamers without conflicting with any regulations regarding color use. The other colors listed, red, orange, and yellow, are often restricted in specific contexts because they can cause confusion with game signals or other equipment on the field. Having a distinction in color helps maintain clear communication and ensures that all participants on the field understand the purpose and positioning of these streamers. Thus, blue is the correct answer as it adheres to guidelines for designating colors on the field without causing any potential confusion.