As well as defining the various stop categories, the harmonised standard EN ISO 13850 also defines the relevant principles for design regarding the colour specification of an emergency stop pushbutton. An emergency stop pushbutton must be clearly identifiable, easily visible and quickly accessible. For this reason an emergency stop must strictly be red on a yellow background.
In accordance with EN 60204-1:2019, 10.2 Actuators, BLACK, GREY or WHITE are the preferred colours for an area stop pushbutton. Under no circumstances may it be the colour of an emergency stop pushbutton.
Additional comment:
In accordance with DIN EN 60204-1:2019, clause 9.2.3 STOP stipulates that STOP functions shall be provided as indicated by the risk assessment and the functional requirements of the machine.