It was in TK Maxx where I purchased my purple and red ones, and since then, they've become faithful fashion friends and definite wardrobe staples. More recently I got some orange ones from Dorothy Perkins. Thanks to Limeyland's consistently grim climate, I am wearing them all the time. I remember the first few times wearing them, I felt a little self-conscious of the vivid hue of my hosiery, but soon became completely accustomed to it.
Ultimately, I aspire to have a beautifully organised sock index like Sherlock's, though mine will contain tights and socks of all colours, textures, patterns and lengths. For some reason I don't think Sherlock will own tights.