Gromski

Why are they green on the inside of the car and amber on the outside?

SWRTWannabe

Because the ones outside have been in the sun and ripened, silly

I guess on the outside, the idea is that they are bright so that they are easily visible. On the inside however, they need to be less obvious as when you are maneouvering (sp?) the last thing you want is to be dazzled by your instrument panel. Orange / yellow is also more associated with a warning too.