Before matching colors, you need to establish a standard source of white light. I strongly recommend using a light table to match colors. All of the color slide combinations in the Insulator Index were obtained using a light table with "full spectrum" fluorescent tubes.
What is a "Full Spectrum" tube?
There is a new generation of fluorescent lamps available that feature extremely high CRI values. CRI is a unit of measure that defines how well colors are rendered by different illumination conditions in comparison to a standard such as daylight. For color-matching purposes, I recommend using a lamp with CRI values of 90 and above. There are a number of "full spectrum" tubes with a CRI of 90 and color temperature of 5000K (such as GE 'Sunshine' lamps) which are available at most retail stores in 18", 24", and 48" lengths.
Using a Light Table
A small light table is a convenient source of illumination, and you can use it any time of the day or night! Place the specimen on its' side on the light table, turn it on, and match your colors - it's that easy! You can build your own light table for about $25, or purchase a commercial one from $28 to $100.
"I used the table tonight as a light table for taking photos of insulators and I could not believe how well they came out. They look the same as what they do when you hold them up to sunlight. I have used other lights and setups, but a lot of the colors just do not look the same as what they do in the sun. I am definitely a true believer in the full spectrum lights. They simulate sunlight quite well. " - John Keener