Do warning signs near a school need to be fluorescent yellow/green or can they stay yellow?
The color of the sign depends upon the sign. Only certain signs are allowed to have fluorescent yellow-green backgrounds. These are limited to pedestrian warning, bicycle warning, playground warning, school bus and school warning signs.
For school signs, such as a school crossing assembly or school bus stop ahead, the background shall be fluorescent yellow-green. Most typical warning signs, such as curve signs or stop ahead shall have a yellow background. Some signs, such as a playground or bicycle sign, could be either color, but if they are being placed because of the school, use the same fluorescent yellow-green background as the other school signs. While not required, the same color will emphasize the relationship to the school.
If you have a stock of older yellow school signs that you had before January 2010, you can use them for a while (see QA on old signs). However, as new signs are ordered, they need to be in the new fluorescent yellow-green color. It is better if all of the signs for a given school zone are the same color so replacing single signs would best be done with the same colors as the existing signs. Once you decide to replace a few signs in a school area with the new fluorescent yellow-green, it may be best to replace all of the signs with the new color and use the existing yellow signs as a short term replacement stock for school zones that are still yellow. Be sure to check the retroreflectivity of the existing signs to be sure they meet the standards.
New York State Vehicle and Traffic Law, Article 33, Section 1219, “Putting glass or other injurious substances on highway prohibited”