Last night I printed the yellow. You can see in this picture that some select areas are now showing -- feathers, specifically. The yellow will be for the bills, and will also support the next color, a bright green for the drake's head.
I am trying to get the brightest colors I can to really demonstrate the vision of a sunny day. I'm hoping the yellow won't be too garish, but choosing a very bright yellow will keep me focussed on keeping the other colors bright.