Gray hair serves as a 'highlight' as well, and adds, I think, more realism. Lets face it, some of the most tell tale signs of wig-ism is when a man has that Spanish-TV soap opera too dark dyed look in his hair & facial hair.
I think folks should really embrace the gray, as it's a highlight that syncs up better with most lifestyles & looks more in line with most of the social circles that the 35+ age group moves in.
That said, when people are in the 1b color range or darker, do the blonde highlights look odd? Are they ever combined with gray percentages as well?