In my experience, I have found the putting another color under yellow is a huge advantage. I used to paint full size cropdusters, they were bright yellow,(Airtractors) We always undercoated with a base of white. It really doesnt take a 100% coverage of the white to make a large gain. However, the white doesnt generally cover well if you have primer spots here and there so I would recomend a coat of light gray to even out the color, then a coat of white, just enough to make it lighter, then your yellow. just my opinion. I have even done some things like putting an orange base coat down, then the yellow, the yellow being semitransparent allows a cast of orange to come through the yellow. But in answer directly to your question, yes put down a light color that covers well.

On the other hand, white is easily the heaviest color so go easy as noted.