On the properties of red exposed to sunlight

I don't know how long this sign has been up in the car park at Waitrose in New Malden. If you stand close - you can't see it here in this blip, it's so faded - you can tell that in addition to the stop hand, there were once words on the sign reading "No Admittance". The sign must have been put up for health and safety purposes to keep people out of the loading bay behind this wall, or at least to act as cover in the event of somebody getting in and being injured. The lawyers could always say - "well, the neceassary signs are there, and you ignored them. We accept no liability".

So what does this mean now? I'm wondering if the same get out is available if the sign is there but the words are not ligible?

Just a thought...