The symbolic meaning in the Elizabethan era was renewal and hope

Yellow is a primary colour 

It’s one of the colours of the rainbow

On the visible light spectrum yellow has a wave length of about 570 nanometers

In psychology yellow suggests happiness

In the 17th Century painters used Indian yellow made from the concentrated urine of cows that lived on nothing but mango leaves

Yellow has a stimulating effect on the mind

Taxi entrepreneur John D. Hertz painted his taxis yellow based on a University of Chicago study that claimed yellow is the colour most easily seen at a distance.  It seemed to catch on!

People notice yellow quicker, even from the corner of their eye.  Lateral Peripheral vision for detecting yellow is 1.24 times greater than it is for red.