During breeding plumage, adult red-necked grebes display a distinct black and white pattern. They have velvety black heads, necks, breasts, and bellies, which transition sharply to dull black on the back. This dark plumage contrasts sharply with a white rump and tail above, as well as white vent and undertail-coverts below. The upperwing pattern is distinctive, featuring mostly pale grey with a broad white leading edge on the innerwing, a dusky grey wedge on the outer primaries, and typically a dusky grey bar on the secondaries. The underwing is pale grey with black coverts providing contrast. Their bills are black to dark red, with red at the base, while their legs and feet are red, and their eyes dark brown. Breeding females are slightly less intense in color compared to males, showing a duller black hue with a greyish tone. In non-breeding plumage, adults exhibit white heads and necks with a neatly patterned black and white-streaked cap. They have a black notch or band behind the eye and ear-coverts, along with a small black patch in front of the eye. Their upperparts and tail turn grey, with a white rump and sides of the tail, and they retain dusky markings on the outer primaries and a dusky secondary bar on the upperwing. The underparts are predominantly white with a faint dusky edge on the underwing and often a black line along the tips of the greater underwing-coverts. Their bills are black, and their legs and feet are dark red. Juvenile red-necked grebes resemble non-breeding adults but can be identified by a wholly black cap streaked with white only at the border with the white forehead. They have a brownish-black saddle, paler and diffusely scaled, contrasting with a mostly pale-grey upperwing. Their rump is white, and their uppertail-coverts and tail are pale grey, similar to non-breeding adults. The juveniles’ underbody is white, and their bills are black-brown with a paler, sometimes reddish base. Their legs and feet vary in color from red to reddish brown or brownish orange.