In its first episode of the new year, called “Shades of Gray,” Homicide: Life on the Street (Friday, January 8; 10 to 11 p.m.; NBC) recovers some of the exalted form – and the signature ambiguity – that even executive producer Tom Fontana seems willing to admit it’s been missing in the post-Andre Braugher era. We get a race riot in which a white bus driver is stomped to death after he’s run down a pregnant West Indian immigrant while shouting at a couple of black passengers to turn off their competing ghetto blasters. Except that everything’s more complicated – island music versus hip-hop; Jamaican newcomers versus long-time-resident African-Americans; a crooked white cop who may have used the chaos of a total social breakdown as a convenient cover to waste a witness; the color-coded blinkers in the cops’ own bunker; even multicultural disdain (like “those Northern Italians who think they’re Swiss or something”) – which is why Giancarlo Esposito ends up saying, “Sometimes I get the feeling that this city has grown subtle on me.” The series always has been.