Red is the oldest pigment in human use and the easiest to obtain, and both facts shaped everything that was later said about it.
The base is ochre, iron oxide, which occurs as coloured earth and needs only grinding. Ochre-processing equipment has been recovered from Blombos Cave in South Africa in deposits around a hundred thousand years old, and ochre appears in burials, on rock surfaces and on bodies across every inhabited continent. Nothing else in the palette is that available, and a colour that any community can make is a colour that every community can use.
Above ochre sat the expensive reds. Cinnabar, mercury sulphide, ground to the pigment called vermilion, gave a brilliance ochre cannot and carried the hazards of a mercury ore. Red lead, minium, was cheaper and darkened over time. For textiles the choices were madder, a root dye known across Eurasia, and the insect reds, kermes and later cochineal, which cost many times more.
That range is why red does not carry one meaning. The ochre red of a burial and the vermilion of a manuscript initial and the kermes scarlet of a cardinal's robe are the same hue reached at wildly different cost, and the social weight of the colour in any given context depends on which one is meant. A tradition that reserves red for the powerful is talking about the dyes. A tradition that puts red on everyone is talking about the earth.