Even in traffic lights there seems to be ambiguity about the colour, amber or yellow. Look at the Wikipedia entry:
Quote
The amber light warns that the signal is about to change to red. In a number of European countries – among them the United Kingdom – a phase during which red and yellow are displayed together indicates that the signal is about to change to green.[4] Actions required by drivers on a yellow light vary, with some jurisdictions requiring drivers to stop if it is safe to do so, and others allowing drivers to go through the intersection if safe to do so.
A flashing amber indication is a warning signal. In the United Kingdom, a flashing amber light is used only at pelican crossings, in place of the combined red–amber signal, and indicates that drivers may pass if no pedestrians are on the crossing.

Peter

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