Sourced from The universe in 100 colors: Strange and wonderful colors from science and nature by Tyler Thrasher and Terry Mudge. September 24, 2024, Sasquatch Books. Published with permission.
Enjoy the first color – not the first in this book of course, but the first color in the universe. This brightly glowing, peachy orange didn’t exist until about 380,000 years after the birth of the universe, when it finally cooled to a comfortable 3000 Kelvin or 2727 degrees Celsius (4938 degrees Fahrenheit): cosmic tank top weather. Before this period, the plasma composition of the early universe was too dense for light to travel. That would require sufficiently low temperatures for atoms to form before the universe could hope to produce anything that could be defined as color.
Today, the average temperature of the universe is just below a cold 3 Kelvin, a steep drop from the original 3000 Kelvin. This was derived from research into the cosmic background radiation, a blueprint of the universe left behind after the Big Bang. The early universe had an evenly distributed temperature with wavelengths attributed to a black body: an object or thing that exhibits color based solely on its temperature rather than the material it is made of. If humans had been able to observe this color as it permeated the space-time of the early universe, it would be comparable to a warm orange campfire. That bright orange would slowly darken and fade until the universe was about 100 million years old, when the first stars were born, resulting in the universe we know today.
If you want to read more from The universe in 100 colors: Strange and wonderful colors from science and naturesee Animals Only See in Black and White and 5 Other Color Myths.