If you want to experiment with colour temperatures, grab the Honl Colour Correction gel kit or similar. It has various strengths of CTO (toward tungsten), CTB (toward daylight) and green (fluorescent tint) gels.

While the flash does transmit the temperature information of the light it produces, it is usually around the temperature of the Daylight white balance setting, which is what most flashes are designed to produce. When you are shooting raw, you can easily change the white balance of the image to warm the image or skin tones, or cool them if the light temperature is too warm.

A CTO (colour temperature orange) gel will shift the light towards the colour produced by tungsten (since it is cooler, it produces a more orange light) whereas a CTB (blue) will shift the colour temperature of your flash past daylight (a hotter temperature, therefore more blue). If you, for example, use a CTO gel and set your camera white balance to Tungsten (~3200K), you will see approximately white light produced in the image.

A full CTO gel is often used to equalise the colour difference between an indoor tungsten light and a flash if they are both used in the same scene. Alternatively, using a mixture of CTO, none and CTB gels you can create a significant difference in colour temperature between your subject and the environment/background.

Here's an example of my using colour correction gels to create a warm environment but using mostly white light in my key light. I used a full CTO gel on the rim light and a normal daylight flash as the key light on the right.