Warm light sources have a lower colour temperature (2000-3000K) and display light across the spectrum of orange, red, and deeper yellow. It is no coincidence that the light from a stove or log burner is inviting, the colour of fire itself invites warmth. You must only imagine the relief that fire gave to early humans, huddled together around a fire in a dark place. That is why we associated orange light with warmth, and protection – it is ingrained in our DNA, over generations and generations.
It is also important to mention that this same spectrum, used to measure light, is also similarly used to measure time in cosmology. For example, the oldest stars in the Universe are Red Dwarves; they have been burning for so long their white-hot temperatures have long died off. This is the slow ember of a dying light – but it still conveys warmth and cosiness.
Cool light sources have higher colour temperatures, more than 4000K. These types of lights have more light in the blue light range – this reminds us of the sky on a very clear, crisp, blue morning. You can emulate this light in any room, especially a room with a lighter décor of blues and white. Returning to the point above about cosmology, some of the brightest stars in the Universe radiate blue light. We associated blue lights with safety, alertness, openness, awareness. Again, it makes sense that Emergency Services use blue lights.
In fact, colour changing lights also use ‘blue’ to help support awareness and create reassurance.