Hello rubaty, very deep and philosophical question. I think the first men discovered these colours as they are easily found in nature: the blue of the sky, the purple of certain flower. Besides, the rainbow contains those colours (actually cyan that is light blue), so I am sure the prehistoric men knew these colours already!
All colours come from white light, which actually contains many many different colours, but because of the limits of our human eyes (the amount and types of rods and cones within our eyes), we can actually only perceive certain colours – this is also why many people see the same colour differently!
Great question again! you re doing great rubaty 🙂 Blue and purple are colors of the spectrum that was first identified by no other than the great man himself: Sir Isaac Newton in 1672! It’s simply a combination of two colors, red and blue. These colors, however, have long been used as a primary dye color for clothing, rugs, pottery, etc by the Egyptians and by many other empires way way before Sir Newton… so while Newton was the first to describe these colors, he wasn’t the first to use them. Hope that helps answer your question 🙂