I live just a couple blocks from Colonial Drug, and have been there many times (I actually just barely missed making the acquaintance of a visiting Australian Basenoter there one day last year). Definitely a good place to find hidden treasures, but it's quite disorganized. Also, be forewarned that much of their stock sits on the shelves for years. I bought off juice there once (got a refund though), so ask a lot of questions before ordering. Prices can also be quite dear; rumor has it the proprietor (her name escapes me at the moment) literally travels to Europe and brings merchandise home in her luggage, a pretty cost- and labor-intensive way of stocking the shelves.
Nonetheless, if you are trying to track something down and just can't find it anywhere (especially feminine Creeds it seems), it's certainly worth a phone-call.