There's more to color than meets the eye, and that's the specialty of a Reston company.

Hunter Associates Laboratory Inc. makes instruments used by manufacturers to ensure the quality and uniformity of their products' appearance:

* An appliance manufacturer found out why a retailer claimed that a shipment of color-coordinated appliances wasn't color coordinated. The manufacturer was matching colors visually under incandescant lighting, while the retailer was viewing the results under fluorescent lighting. Their differing assessments were due to metamerism, the phenomenon whereby colors may match under one kind of light but not another.

* A vintner learned what blends of grapes gave the wine enough clarity to keep customers coming back.

* An auto company matched colors of parts made in different parts of the country.

Among Hunter Laboratory's stranger assignments have been running color tests on samples of bird beaks for a university, measuring color variations in the aluminum exterior of New York's World Trade Center and the glass exterior of a building in Tyson's Corner, and helping a hospital make artificial limbs match natural skin color.

The company was founded in 1952 by Richard S. Hunter, a veteran National Bureau of Standards expert in appearance technology who had designed a uniform color scale utilizing numerical values. Hunter had followed his NBS service with a stint as chief optical engineer for the Henry Gardner Laboratory in Bethesda.

He started out by working from his home in McLean, specializing in testing and consultation in appearance measurement, but switched emphasis to instrument manufacture in 1956, when Procter & Gamble Co. needed 26 instruments for measuring the color of its soaps.

HunterLab, as the company is known, grew slowly but steadily, and today its 120 employes produce appearance-measuring instruments, engage in research and development, run seminars, and trouble-shoot for major manufacturers. The company is active in more than 60 countries, according to Nick Papadopoulos, HunterLab's marketing director.

Richard Hunter was succeeded as president in July 1981 by his son Philip, who joined the company in 1973 after four years of financial work with the Air Force and three years as financial analyst for Nuclear Fuel Services Inc.

Philip Hunter and Papadopoulos estimate that more than half of the manufacturers of consumer goods in this country use color-measurement devices made by HunterLab and its four or five American and eight to 10 foreign competitors.

The elder Hunter has endowed a professorship in color science, appearance and technology at Rochester Institute of Technology and is continuing his research into measurement appearance at HunterLab. His Hunter "L,a,b scale," developed in 1958, measures colors according to their place along three axes: black to white, red to green and yellow to blue.

HunterLabs' instruments determine an object's chromatic (color) and geometric attributes (gloss or haze) by measuring light that has passed through or has been reflected from an object.

In colorimeters the light then passes through a series of four filters, each of which allows some of the light to strike a photodetector. The photodetector expresses the intensity of the light as a number. The filters represent a color-measurement standard developed in 1931 to duplicate the way the eye sees colors. The colorimeter then can convert these values to the values of other color scales.

Spectrophotometers measure the wave lengths of the light at defined intervals of the visible spectrum, also using photodetectors.

Glossmeters determine the luster or mirror-like appearance of objects. Their photodectors measure the light after it reflects off the object.

Haze meters determine the degree to which a nearly clear object scatters light it is transmitting or reflecting. HunterLabs' newest product is LabScan, a spectrocolorimeter, which combines colorimeter and spectrophotometer functions.

In the late 1920s and early 1930s at the NBS, it took Richard Hunter half a day to make a color measurement and another half a day to analyze the resulting data. His company's instruments now perform the same functions in 1.6 seconds.

Philip Hunter sees the science of appearance measurement advancing in the next year or two to the point where "we can take something into a paint store and say, 'Here, match this,' " and they will be able to do so to the extent that no one will see any color difference.