General aviation pilot reported the aircraft ran off the ramp at VAY; citing uncharted construction changes as contributing.

Narrative

Ran off ramp south of Taxiway Delta. No taxiway identifiers led to a loss of positional awareness. Construction on the ramp relocated a taxiway and was not reflected on the charts. Attempted to return to starting point on airport and mistook a dark patch of mud for pavement. Aircraft then became stuck in the mud south of the east-most ramp. Aircraft towed out with no damage of any kind. No injuries sustained.