Joe, good question. Fall/winter - male dull grayish bill. Female, similar to male but cheek crossed by dark line. In May, not sure about this. See what others say.
The changing color of soft parts like bills and legs are highly driven by hormones. For example, you can easily find very bright yellow/pinky legs, rather than plain pink, on some Herring Gulls every spring in NJ. This is not generally illustrated in the field guides.
This bird might be second year or simply may have lower than normal hormone levels for some reason. Either could explain the lack of a blue bill.