Orange and lavender spots?

My daughter is just finishing the class room portion of Driver's Training.  On the way home last night I was quizzing her on what different signs and signals mean and what you're suppose to do.  She was doing pretty well until I posed this questions to her...

 

When the light is green you go.

When the light is red you stop.

But what do you do

When the light is blue

With orange and lavender spots?

~Shel Silverstein 

She had never heard that poem before and gave me a strange look.  I told her to ask her driver's ed teacher for his advice.