Someone told me red is shorter so we see it faster -- is there any biological evidence for this?
It's pretty rare to see red in nature that isn't blood or fire, and when you do it's often on dangerous things (like those frogs in the amazon). Maybe red is so striking to us because red things in nature are things we need to pay attention to?
The speed of light is constant in a vacuum, but different for different wavelengths in a medium. This is why shining white light through a glass prism causes it to disperse into many colors -- they each travel through the medium at slightly different speeds. Interestingly, the refractive index (how much the light slows down in a medium) is higher for larger wavelengths like red in the color spectrum. So technically, red light travels slower than blue or green light in a medium (eg. air, water etc.).
Of course I would delays in this would be absolutely tiny compared to delays due to neural processing .... but hey who knows, maybe we can tell the difference!