Blood pressure
Red is used often in signs to alert danger or grab your attention, hence say a stop sign or a firetruck are pretty much universally red. It is believed, psychologically, the colour red conveys strong emotions conveying conflict or aggression. Some studies have suggested exposure to the colour red is linked to the raising of blood pressure and metabolism.
First colour
In the first few weeks of life, a newborn can only distinguish shades of black and white. After a certain time the first primary colour they observe is the colour red. Red will be their only colour for several months until they start to contrast between red and green when they are 3 to 4 months old.
Bug pigment
There are many ways to make the colour red. A very old and unique version is the harvesting and smashing of cochineal insects in Central and South America. When smashed and powered the insects make for a deep red pigment. This was invented in the 1400s by the Aztecs. To produce one pound of this dye requires 70,000 cochineal insects and they all live in prickly pear cacti.
