Older Chinese characters tend to be simpler. You can use this to measure the relative ages of ancient concepts.
For example, the Chinese characters for RYB colors are:
The simplest characters are written with a single radical. The oldest radicals are all Kangxi radicals. White 白, black 黑 and yellow 黄 are all written with a single Kangxi radical. The other colors contain at least two radicals.
This fits almost perfectly with Lazarus Geiger’s evolutionary progression which goes black and white ➝ red ➝ yellow ➝ green ➝ blue. The only color out-of-place is red 红.
Wait a minute...I can't recall ever encountering the character "红" in ancient Chinese poetry.
That's because "红" is a relatively new character for the word "red". The traditional five colors 青黄赤白黑 use the Kangxi radical "赤" for red instead of "红". Mystery solved!
If we use the ancient character "赤" for red instead of the modern character "红" then the first four colors in Geiger's sequence are all single Kangxi radicals and the rest are all composite characters with at least two radicals.
It gets better. Did you notice how we've only used four of the five colors so far? Take a closer look at the five colors 青黄赤白黑.
This list includes qīng 青, the color of nature, spanning blue and green. It is the 5th and 6th color in Geiger's progression. Qīng 青 is written with a single Kangxi radical.
If all you have is black, white, red and yellow then creating a new color for blue and green is the natural progression.
Bastian also argued that Tagalog speakers in the Philippines had not even distinguished between green and blue until the arrival of the Spanish colonizers, because the Tagalog words for “green” and “blue” were clearly recent borrowings from Spanish verde and azul. And he claimed that the language of the Teda tribe in Chad still did not distinguish green from blue at all
― Through the Looking Glass: Why the World Looks Different in Other Languages by Guy Deutscher
Today, qīng 青 is used in more poetic contexts while green 绿 and blue 蓝 are used in less poetic contexts.
 For more information about Lazarus Geiger's work, see Chapter 4 of Through the Looking Glass: Why the World Looks Different in Other Languages by Guy Deutscher. ↩