FAQ: "We are looking for a lab who can do a fairly advanced type of color check. We powder coat our shingles with blends of three colors. In addition the blends are applied over a base color that is different from any of the three colors in the blend. Do you have any color equipment that could grid off a section of one of our powder coated shingles and measure the quantity of each of the four colors involved? We are trying to determine whether the percentages of each color are changing therefore giving us a different appearance. We can provide Lab values for each of the colors involved. Please let us know whether Hunter can do this and if so the cost of the test."
What you have identified is color quality control on a roofing shingle that is a spatial arrangement of 4 colors (base with show through + 3 color bend).
Typically colorimetric color control is performed by measuring individual granule colors as they present a more uniform color for precise color measurement. Also, typical colorimetric instruments optically average everything within the field of sample view.
What you need is an imaging system that can do a RGB multi-color comparison of a good shingle in comparison to an unacceptable one with a focus on the number of granules for each color and the randomness of the pattern.
Unfortunately we do not know of a testing lab that can do this type of testing. I would suggest you contact the following supplier of industrial imaging systems:
Natick, MA USA
Your input imaging device could be a simple as a scanner but may require a high definition camera and fixed lighting to count the granules of different colors.