Hi Paul, I found this, I hope it clarifies it for you. According to EN/IEC 60947-5-5, EN/IEC 60204-1, and EN ISO 13850, buttons used as actuators of an emergency stop device shall be coloured red. When a background exists behind the actuator, and as far as it is practicable, it shall be coloured yellow. Most suppliers of push buttons accomplish the yellow background in one of three ways: 1. Use of a yellow enclosure. 2. Use of a large Emergency Stop legend that is yellow. 3. Colouring the “stem” of the push button yellow. Note: Use of a yellow guard is also accepted in some industries, though this is not typically allowed. This will be discussed in more detail later in the paper.

If it isn't an E stop, then I imagine that its just a general feature and will not be subject to the specifics. I would say that it doesn't need to be red with yellow etc. As long as it does have an E stop (which you said it does) and that is clearly marked up as aforementioned, then I would leave it as it is.

If it is not an e-stop your stop button should still comply with PUWER regulation 17: "....ensure that all controls for work equipment are clearly visible and identifiable, including by appropriate marking where necessary". The Approved Code of Practice gives this guidance: >> Clear identification of controls It must be possible to identify what each control does and which equipment it operates. There are several well-established ways of doing this: - by the design and shape of the control; - by labelling or marking; - by the layout of controls on a panel or console (grouping controls according to their function). It is unlikely that any control will be adequately identifiable without some sort of marking. << So mark or label it so that it is obvious what stops when it is pressed. John