Field & Stream occasionally launches discussions about pink guns on their website. I've linked to some of them below:
Sep. 25, 2007 Field & Stream "Field Notes" blog had a post titled Manufacturers Roll Out Pink Guns For Women
Nov. 27, 2007 The "Field Notes" blog had a post titled Pink Guns Flying Off The Shelves
April 7, 2008 The "Field Notes" blog had a discussion topic titled Do Pink Guns Look Like Toys?
I was reminded of these discussions when I flipped through the latest Gander Mountain flyer and went "Awww...how cute!" over two pink guns that were on sale. My personal take on pink guns is that they are kinda cute - but not realistic for actual hunting.
(At the time of this post)...I (could) only find two manufacturers who make pink guns: Remington (two) - Model 870 Junior 20-Ga. (Gander Mountain exclusive) & Model 597 .22LR Rimfire Rifle; Keystone Sporting Arms has a LOT of pink .22 rifles including - Model 226 Stainless Steel, Model 225 Blued, & Model 221 Stainless Steel (Clearly since this post, there are MANY more manufacturers of pink guns!)
Other than that, you'd have to get a custom gun. Jim's Gun Supply was mentioned in the orignal article discussed at Field & Stream. Here's a link to his website for custom work - he customized the pink Glock in the photo.
Interesting article here and here and here.