And this doesn't just happen at congested intersections, it happens everywhere. Now I complain when my brother pulls up practically on the bumper of the car in front at a light, but a couple feet is usually the norm. A car length and a half is STUPID!
Mood necklaces or rings usually contain a chemical that changes color with heat (example cold to warmer black, purple, blue, green, reddish). They then usually have a pamphlet saying what the colors mean.
Recent images from the Cassini spacecraft now orbiting Saturn confirm that different rings have slightly different colors. The above image shows their sometimes-subtle differences in brightness and color. The rings reflect sunlight and so, even if they were perfectly reflecting, would appear the color of the Sun.