From NFPA 72 (2010 edition)
17.14.1 - Manual fire alarm boxes shall be used only for fire alarm initiating purposes
17.14.1.1 - Unless installed in an environment the precludes the use of red paint, manual fire alarm boxes shall be red in color
17.14.1.2 - Manual pull stations for initiating other than fire alarm shall be permitted if the devices are differentiated from the manual fire alarm boxes by a color other than red and labeling
17.14.1.3 - Manual fire alarm boxes shall be mounted on a background of contrasting color
17.14.5 - Manual fire alarm boxes shall be installed so they are conspicuous, unobstructed, and accessible
One thing I have noticed within the past decade is the increase use of card access door systems that need to have an emergency release on the secure side of the door in case the “Request to Exit” device fails to operate. You can also have generator shutdown or HVAC shutdown switches that look exactly like a fire alarm pull station. These “non fire alarm” pull stations are yellow, green, or blue in color. I think the intent that NFPA is trying to put out here is to reserve red as the color for the fire alarm system.