1) have them cleaned before they maul you, or
2) change out of work clothes before exciting the vehicle
Lesson learned. Fortunately I just wore nice jeans today and not something more delicate. Suit pants don't hold up as well to blue, yellow and pink chalk as a pair of Express jeans might.
On a side note, thoughts and prayers with the folks in Japan today. Living in Southern California this kind of thing is on the back of our mind all the time, and I can't imagine having the nightmare actually become a reality.