TieDye extends the dye list in the costume window with options to help make finding dyes easier.

Features

Display dyes in a grid or using a long listing showing the dye gradient and name
Show names for unknown dyes. Thank you to the author of DyePreview for the list!
Search for dyes by name, color, or cost
Sort the list of dyes by color index, dye name, or cost
Show all dyes or only those you've unlocked (shows all possible colors, these may or may not be available in game)

Not all dyes are available at this time, and there are a few that have no names at all currently.

Planned Features

Sort dyes by collection
Show where dyes can be found

Other Addons (not by me)

DyePreview lets you preview dyes you don't have yet
DyeTracker gives you a simple UI for seeing which dyes you have and don't have and where you can find ones you don't have yet.

12 August 2014: TieDye was written for one purpose and one purpose only: Make it easier to find the color you want to use when dyeing gear. In this regard the functionality I wanted is complete - filtering and sorting dyes by name, color, and cost. I do have other features I want to implement related to collections and where dyes can be found but right now I don't have the time to work on adding new features to TieDye and these are not directly related to TieDye's job.The addons I've mentioned above make good compliments to TieDye and I suggest checking them out.