Not sure about the biology, but there is some evidence from physics for this. The speed of light is constant in a vacuum, but different for different wavelengt

Not sure about the biology, but there is some evidence from physics for this. 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!