Blue is for bright daylight and iridium for daylight glare. Both reduce the amount of light passing through the lens, so not good for nighttime.
High def yellow is best for enhancing contrast and light in low light applications, but usually not recommended for night driving or bright light environments. I had a pair of yellow eyeglass clip-ons that were designed for night driving, once. They helped reduce the glare and halo effect of oncoming headlights, but overall I didn't like the effects.
For me as much light that can reach my eyes at night is best, so I stick with clear. For bright daytime, I use smoke grey, because it does not distort natural colors. For cloudy daytime, I go with amber (which is actually a good overall color) or rose for enhanced contrast (i.e., fog).
Chris Glennon - Portland, OR