Gandalf, as has been previously noted, still appeared elderly even early in the Third Age. Saruman, however, seems to have appeared somewhat younger, with his hair still black (emphasis mine):
The first to come was one of noble mien and bearing, with raven hair, and a fair voice, and he was clad in white; great skill he had in works of hand, and he was regarded by well-nigh all, even by the Eldar, as the head of the Order. Others there were also: two clad in sea-blue, and one in earthen brown; and the last came one who seemed the least, less tall than the others, and in looks more aged, grey-haired and grey-clad, and leaning on a staff.
Unfinished Tales Part 4 Chapter II: "The Istari"
We can compare this to his appearance following the Battle of Helm's Deep (emphasis mine):
His face was long, with a high forehead, he had deep darkling eyes, hard to fathom, though the look that they now bore was grave and benevolent, and a little weary. His hair and beard were white, but strands of black still showed about his lips and ears.
The Two Towers Book III Chapter 10: "The Voice of Saruman"
Though Gandalf notes earlier in the chapter that Saruman can affect how he appears in the eyes of others, so we have to take all descriptions of his appearance with a certain skepticism.
We don't have enough information to say anything meaningful about the other wizards.