Steve Foster , Sep 06, 2006; 11:55 a.m.
Colour meters are expensive. The way most photographers evaluate colour temperature when shooting RAW (you don't mention if you shoot RAW) is to take a picture of something neutral (a whibal card for example) that is in the same lighting as your subject then take a photo of the subject. Leave your WB on Auto when you do all this. Then when you get home open the picture of the neutral card and use the WB function of the RAW converter by clicking on the Neutral area. This will then make the image of the neutral card exactly neutral (with me so far!) then just copy the WB settings to your other image.
I always carry a whibal with me and take a photo of it every couple of hours to keep in step with the changing daylight temperature. If it is partly cloudy I take one in cloud shadow and one in sunlight.
I know I haven't exactly answered your question but when you can accurately get a WB temperature for a few quid instead of hundreds of pounds then it might be relevant. With normally Digital photography (landscapes, sport, portraits etc. a colour meter is more or less defunct. The only use is probably when you are in one lighting situation but you are taking photographs in another lighting situation (your in the dark at the back of a stadium and your subject is floodlit with sulphur lamps). But in this scenario you can always take the photograph and then when you are home WB a bit of white hording or an advertisement that has white or neutral grey in it, this will not be totally accurate but will normally good enough for most purposes.