Does the colour of the sensing face on cylindrical sensors mean anything?
Generally, the colour of the sensing face is the colour of the manufacturer’s logo, eg. green for P+F, blue for Sick/Schneider, black for Balluff/Omron, orange for Schmersal, etc. But, some manufacturers change the colour to denote a special application, such as 2-wire or oil-resistant. So, it’s best to go by the label, not by the colour.