Definition: A milder version of POS; sometimes refers to a piece of junk, but may also used as an exclamation towards someone else, i.e., in online gaming, when someone sneaks up behind you and kills your character, you might type, POC! Example
You may have noticed that your lips turn purple or blue in the cold, or you may have seen a baby, an elderly person or someone else with bluish or purplish lips. In many cases, this type is caused by cyanosis, which is a discoloration of a part of the body resulting from a lack of oxygen in the blood.
For many cacti and succulents turning purple or brown is a sign of stress. This can be caused by very high temperatures, excessive sun exposure, too less water given or even very frequent repotting (as Kakteen said it may reflect discomfort or problems with the root system) or combinations of these.