Is energy always conserved?

At 0:31 PG states "...as light become stretched-out and becomes a cooler color..." is the first faux pas I've heard her make. There is an ambiguity here: Artistically, red is referred to as a warmer color, but physically it is generated at a lower temperature, lower energy transition. I think you have to be careful here: I've never heard a physicist refer to red as a "cooler" color, usually the phrasing is "of lower energy, or lower temperature but the phrase "cooler" seems to be reserved for the artistic usage. "Color temperature" is also physically orthodox but just saying "warmer or cooler" without citing temperature is an artistic usage faux pas. This is kind of an uneasy "agreement" between physicists and artists that we do our best not to tread upon that which young people might not be aware of.