The Honl Photo Color Correction Filter Kit is a great accessory for your Honl Photo Speed System light modifiers. It allows you to match your flash's light output to the color balance of background lights, so that the room lights visible in your shots will look just as white and clean as the main illumination being provided by your strobe.
The kit consists of a pair of 1/2 CTB filters (to adjust a tungsten light to appear as normal daylight), two each of full/half/quarter CTO filters (which lower the Kelvin color value of your flash to match tungsten lights), and two full CTO + green filters (which match your strobes' output to the color balance of typical fluorescent lighting).
Instead of having perfectly-exposed subjects cast in front of dark rooms, or perfectly-exposed subjects with unnatural orange or green color casts upon the visible background lights, you'll now have the capacity for bright backgrounds with perfect color along with the easily-achieved perfectly-exposed subjects.
The aid of a color meter can help you choose which filter to use, but they're very costly and fragile. The easiest way to achieve proper balance is to have a professional white balance aid (such as ExpoDisc), and first take a color balance reading immediately adjacent to the background light. After setting your camera with that color balance, experiment with the gel filters a few times, examining the skin tones of your subjects on your camera's screen. When you find which gel renders your subjects most naturally, you then take a color balance reading with the gel in place upon your strobe, using the gel + strobe as the lighting source for your balance reading. Set your camera to this balance of color, and you're left with perfect skin tones and background lights which should appear quite natural.
2 x 1/2 CTB Gel Filter
2 x Full CTO Gel Filter
2 x 1/2 CTO Gel Filter
2 x 1/4 CTO Gel Filter
2 x Full+Green Gel Filter