How to measure the color of honey?
Could you use a reference color chart? Here is one originally made for skin colors:



Wikipedia has other examples.
Paint stores might give you a nicely printed color chart for free.

There are also online versions of color selectors, for example the one from Pantone, but then you have to be very careful about color calibrating your screen, or at least not changing it between comparisons.

A third option, more realistic if you are only measuring color along one scale, would be to make your own comparison material. Start with a light honey colored liquid and mix in a darker color till it matches your honey. The amount of dark color used gives you the darkness of the honey. You probably have all supplies available in the art department.

Edit:

MaxW found a much better solution, a special color scale for honey. It is called the Pfund scale: