There is exactly one possible color sequence of the three lights if which one of the following is true?

Emil-Kunkin on August 29 at 11:37PM

This is a fully determined question, albeit one phrased oddly.

We know that if 1 is purple then 2 is yellow, so 2/3 are determined. Additionally, the final rules tells us that if 3 isn't green that 2 is p. This means that if 2 is not p, then three must be green. So, if the first is purple we know the colors of all three.