What Colours are mandatory signs?
What Colours are mandatory signs? Mandatory safety signs (Blue) Mandatory health and safety signs signal the need for certain behaviours. It conveys information that you must comply with to be safe. These signs must be blue and usually have a white symbol on a blue background.
What are the forbidden colours?
Some subjects reported seeing the forbidden reddish greens and yellowish blues. Others saw hallucinatory textures, such as blue glitter on a yellow background.