The only time you should be using pistel colour as any indication, is if the trichomes are coloured. LSD-25 is the first strain I encountered with purple trichiomes, very neat to see. The yellowing of the bud leaves is natural, just cannibalizing itself to use all the nutrients it has left in the leaves. Yellowing near the end of its life is normal, not grower error. If you checked the entire plant and it is uniformly 80% cloudy 10% amber and 10% still changing, then it sure is time to harvest. You can leave it in darkness for up to 3 days to bulk up the trichomes. any longer is not something I would recommend.