Colorcoded map: regional population structures at a glance | R-bloggers
▻https://www.r-bloggers.com/colorcoded-map-regional-population-structures-at-a-glance
For each NUTS-3 region the unique color is produced by mixing red, green, and blue color spectrums in the proportions that reflect,correspondingly, relative shares of elderly populating (aged 65+), population at working ages (15-64), and kids (0-14).
Each of the three variables mapped here is scaled between 0 and 1: otherwise, the map would be just green with slightly variations in tones because the share of working age population is ranged between 65-75% for modern European regions.