“Fine. Go naked. And, Harry, make sure you get a picture of him. Goodness knows I could do with a laugh.”
     -- Molly Weasley, when Ron refused to wear his second-hand dress robes

Traditional Wizard clothing consists of robes, cloaks, boots, and possibly a hat of some kind. The colors are bright and the style somewhat extravagant. 

• Dumbledore, when he arrives in Privet Drive, is wearing long robes, a purple cloak that sweeps the ground, and high-heeled, buckled boots (SS1)
• "people in cloaks" that Vernon spots on his way to work: emerald green, violet (SS1)
• robes have pockets, inside and out (e.g.CS13)
• Cornelius Fudge wears a pinstriped cloak, a violet top hat, emerald green trousers, etc.
• ear muffs are worn (Dumbledore remarked that he had blushed when Madam Pomfrey had complimented him on his pair (SS1)), and not always in winter: Sprout provided them for her Second Years to protect their ears from the cry of the Mandrake. These must have been enchanted, since normal earmuffs don't block sound entirely (CS
• Rita Skeeter wears acid green robes (GF20)
• students at Hogwarts wear black pointed hats to class 
• "Snape said Moodys searched his office as well?"  Ron whispered, his eyes alight with interest as he Banished a cushion with a sweep of his wand (it soared into the air and knocked Parvati's hat off). (GF26)
• Neville's grandmother wears a long green dress with a fox-fur scarf, a tall hat with a stuffed vulture on it, and a big, red, handbag (PA
• dress robes - students of fourth year and above are required to have dress robes to wear to formal events. Molly Weasley gets Harry some very nice ones, but is forced to buy dress robes for Ron at a second-hand shop. His are frightfully out of style, with lace at the collar and cuffs.
• Harry: bottle green
• Ron: maroon (second-hand) with lace which he tried to remove with a Severing Charm.
• Crabbe and Goyle: green (Harry thought they looked like moss-covered boulders)
• Pavarti Patil: shocking pink
• Padma Patil: bright turquoise
• Fleur Delacour - silver-gray satin
• Malfoy - black velvet with a high collar, which in Harry's opinion made him look like a vicar
• Pansy Parkinson: very frilly robes of pale pink
• Hermione: floaty, periwinkle-blue material
• McGonagall: red tartan and a rather ugly wreath of thistles around the brim of her hat
• Ludo Bagman: bright purple with large yellow stars
• Madame Maxime: flowing gown of lavender silk
• Percy Weasley: brand-new, navy-blue dress robes

• Madam Malkins Robes for All Occasions
• Gladrags Wizard Wear
• used robe shop in Diagon Alley