It seems obvious to me that colors came before color vision. Natural selection constrains diversity along the axes that it selects for, while genetic mutations supply diversity along all axes simultaneously. The net result would, intuitively for me, be that nature must have had the colors before anyone could see them, since there was no reason to constrain having colors.
We'll see if that ends up being anywhere close to correct.
It turns out I didn't grasp what the authors meant by "colorful signals". They're talking specifically about vivid colors that serve an evolutionary purpose, and in that case it seems rather clear that vision would have to come first. That is in fact also what turns out to be the findings.
While the article is a fun and light read about some scientists doing some literature review to try and approximate when color as a signal evolved, I'm afraid the error bars are so large it's hard to find any certainty.
The article does end with some speculation that vivid color can't actually evolve without eyes that produce a natural selection bias, since vivid color takes effort to construct. That claim of course has the same efficacy problems as what the article is mainly dealing with, but I do find it somewhat convincing, and have lowered my certainty that vivid colors actually evolved first.
From TFA:
"Color vision likely evolved twice independently, [Wiens ] found, and around the same time: between 400 million and 500 million years ago in arthropods, such as insects, and in backboned animals, such as fish. That places the evolution of color vision 100 million or 200 million years before any color signals."
"Wiens and Emberts’ data supports the hypothesis that color evolved for some as-yet-unknown reason before any of these flashy signals. “It was color vision first, then fruit, then flowers, then warning signals and then sexual signals,” Wiens said."
As such, many colors would be expected in environments that don't confer an advantage to colors. And once an environment starts to give advantage, you would expect rapid convergence.
Which, maybe I'm just reinforcing old learning of mine? Moths were a specific way of teaching evolution in my grade school, and they acted exactly as I just described. With soot covered areas growing rise to black colorings and cleaner air giving rise to the opposite.
There's color in nature beyond life, such as in minerals and other chemicals. There's also color in life that isn't necessarily meant to convey something —such as the green of plants or the red in blood— that could be useful for finding food, for example. Interestingly, hemoglobin seems to have come to be > 400 mya too [1].
Moreover, color can help with contrast in vision. Two materials could reflect the same amount of light, but in different wavelengths.
[1]: https://www.ox.ac.uk/news/science-blog/ancient-blood-lines-t...
But yes. Logically, things have a natural color. Then animals progressively acquired the ability to distinguish colors because it was advantageous - for instance to spot a naturally brown yummy insect on a naturally green leaf.
From there, one can imagine an amplification or reinforcement process induced by co-evolution: plants take advantage of the fact that animals can see colors, animals take advantage of the fact that healthy plant produce fruits of a specific color. It eventually turned into an armed race at times: TFA opens with the example of a blue belly lizard, but one cannot help but think about chameleons.
It was probably unavoidable as soon as something like a photo-sensitive cell appeared. And it is also probably the same thing with perceptions that are less obvious to us, such as odors, sounds, or vibrations (other than of air or water - although I wouldn't be surprised if hearing evolved from that point).
Why? I can imagine other chemical compounds with different colors that perform the same function just with a greatly reduced efficiency.
If there isn't any evolutionary competition then there could have been a long period of time before plants with chlorophyll started being produced and then dominating the landscape.
When there's no environmental pressure, genetics can do whatever it wants (to a certain extent), which leads to a diversification which in turn is very valuable when a constrain suddenly appears in the environment, or to conquer new biomes. This remembered me of the "Cambrian explosion" [1] and coincidentally this article refers to the evolution of the eye.
With regard to green chlorophyll, it is safe to say that a very common environmental pressure is present that makes it green, judging from how dominant it is. I guess that it doesn't apply to species that have red/dark red/purple foliage due to their specific ecosystem niche, or maybe an even greater constrain is at play ?
"To be clear, there was color in the world before color vision. Plant leaves, for example, reflect green light even if there are no eyes to see it."
But also keep in mind that green plants are just the ones that won, there are other chemistries with colors that work nearly as well (particularly purple, which is still present on some plants).
Color vision (or just ability to differentiate 2 or more frequencies of light) could have evolved a soon as there were forms of life for who this was advantageous - potentially as simple as an ocean organism orientating itself towards sunlight.
It seems the co-evolution of the property of color and color detection ability in plant and animal species, must logically have followed a basic ability to differentiate non-evolved natural colors.