As a young man many years ago, I had dark brown hair with a mild "Eddie Munster" peak (actually a cowlick, but that's another story). As my hairline receded in my late 30s/early 40s, the peak formed a peninsula, which finally broke off to its own island by my early 50s. Now in my mid-60s, I'm bald on top and thin all around. I cut it with a zero guide, so its pretty tight to my scalp. I'd say about 2/3 gray, 1/3 my natural color.
I wear a goatee year round, but have been letting it grow into a full beard October through April(ish - if it gets hot early, I'll shave back to the goatee only). The goatee is about 90% white, with the dark brown concentrated on my chin, so that I have a Fu Manchu look, which I rather like. The rest of the beard is probably 65%-35% white/natural.
Of course, the supreme being is punishing me for any vanity I had in my youth, as she has compelled me to trim hair from my ears and nostrils on a pretty much daily basis.