Well there is the Broncolor FCC.
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In general, you can't. "Color temperature" is about comparing the hue of an ideal black body radiator to the light source you are trying to characterize. In this case, it's trying to compare apples to concrete blocks. Fluorescent light is discontinuous, and the spectrum emitted typically has huge peaks and valleys, not found in the spectrum of an ideal black body radiator. The quality of light between the two sources is incomparable.
In practice, a color meter basically looks only at the orange-blue axis, and tells you where the light ends up on that axis. Most color meters tell you nothing about the magenta-green axis. Unfortunately, that's what matters most with cheap building fluorescent lights, because they tend to produce the majority of their light via a huge green spike. This is the reason many video cameras show you a sickly green color cast even when you set their "color temperature" to the correct value (say, 6500K for a "daylight" tube).
For this reason most modern video cameras include a manual white balance function that makes many measurements, including the dreaded magenta-green axis. A good manual white balance made against a calibrated gray target (think 18% Kodak gray) will generally give you fairly accurate color without a noticeable color cast in all but the most challenging lighting.
As to human clients visiting your shop... showing your wares under color corrected light will make a better impression. There are good fluorescent tubes out there -- KinoFlo True Match. Westcott. Some others. Very little in T5 except for biax bulbs (2G11 base) which are common in cinematography lighting, but not in building lighting.
Bruce is dead on. The Kelvin scale doesn't even really reflect shifts on the magenta/green axis. There are other methods of quantifying, but to get a meter that can read a fluorescent accurately AND communicate better than a simple Kelvin number typically cost a fortune.
If all you're after is a rough idea, "Pocket Light Meter" for the iPhone includes a Kelvin scale. Not perfectly accurate even for easier to read sources.
Your best bet is to stick a piece of white poster board under one of these lights in such a way that it is not also lit by any extraneous sources and take a picture with it exposed around zone 6 or 7.
Bring that shot into lightroom (or whatever you use) and use your eyedropper tool to balance the shot so that the card is true white. Whatever lightroom tells you your balance is your Kelvin rating.
Mind the handy green magenta slider just below the color temp. (Assuming you are using lightroom) If its strong toward magenta, you lights are green and vice versa.
The Minolta color meter was never very accurate for fluorescents-I used one for decades for architectural interiors. Every film had a different responce-particularly like from Kodak to Fuji. One had to take what it said and "use your experience" with a particular film then also adjust for long exposure color shift etc. The Minolta color meter took none of that into account nor did it have any memory function. It was mainly about testing and experience. It was tedious. I do not miss it. Digital is a dream compared to transparencies with flourescents.
All but the cheap off-shore lamps will print the color temperature on the end of the lamp (you probably call them 'light bulbs'). Go up into the luminaire and pull one down. It probably requires a twist of the lamp to get it out. You should be able to see some markings on the lamp near the socket at one end. The color temperature will be printed there.
However, as has been said, this is only somewhat useful because the green/magenta level will be undetermined by this value, and since the light is a discontinuous spectral distribution, there will still be shortcomings even if you perfectly match up the CT value.
---Michael
Pretty much any digital camera with manual control has K white balance control where you can preset light temp.
Set your exposure. If you are combining flash and constant light it is important.
Guestimate color temp, set it, take pic of white piece of paper. Paper color on preview will be either bluish or redish, based on that select another temp.
Its longer to write - in few iterations you'll get color temp.
Works fine with flash (if you can connect sync cable), thungsten, hmi etc combined all together.
But then again some people have allergy on digital.... even when it helps to take decent film pic
Back to many years ago, one of my hats was as an industrial photographer. I used the Minolta II as a starting point but needed experience to get it right. In talking with the plant maintenance people we concluded that all the overhead florescence bulbs were of the GE "cool white" brand, both in the plant and the office area. I asked that they only replace with this same bulb, which they did. This allowed me to use a magenta 40cc filter on camera with daylight transparency film any where in the building. Worked with strobe flash also. For exec portraits, kept them away from windows.
Tom