When it first appeared, the universe was much warmer, about 3,000 K. The early universe was filled with a bright warm glow.
We have a good idea of what that first color was…. a bright orange-white glow, similar to the warm light of an old 60-watt light bulb.
If we could go back to the period of that first light, we would probably perceive an orange glow similar to firelight.
What was the first colour in the universe?