If you'd like to filter the flash then consider using Rosco or Lee filters from a swatch book. They may be slightly small but some black tape should cover any spill points. They are really inexpensive and allow you to match virtually any light source and offer a wide array of party gels as well. I just tape them to the front of the flash. Correction can be made for any tungsten, mercury vapor, sodium vapor etc.
Different manufactures color correction gels differ slightly in precise color, so it may be prudent to stick with one for precise correction. I actually prefer the CTO colors of the Lee, but they were not widely available when I put my kit together so I went with Rosco. The Nikon version of CTO is slightly different than either and I keep it marked in the Rosco book. I keep a complete book on hand for comparison and to make sure every thing goes back in it's proper place. The bracelet is organized in the original order of the swatch book and the filter names and factor in stops are Sharpied on each filter, with a filter for each of my small flash units.
The bracelet holding the filters is actually a bracelet with magnetic clasp. The magnet is easy to open and close and the filters move easily but not freely past the clasp and around the beadwork. Originally I used a plain wire bracelet and screw clasp which allowed the filters to move readily and quickly along the bracelet. Unfortunately I dropped it once while on assignment and the unrestricted movement allowed filters to spill across the conference room floor. For me this is slower but more controllable. The tape dispenser on the back is hot-glued in place and readily available at office supply stores.