I’ve never been here, but there’s The Color Zone Salon in Gaithersburg. A bit farther from you, but it sounds like what you’re looking for. This is from their website:
“Grey coverage is my number one service requested. I love the challenge of creating a color for you that mimics nature. Whether your goal is to cover your grey or blend and embrace it we will create a plan for you.”
https://www.thecolorzonesalon.com/specialty-services
If you go there, let us know how you like it!