Low wages also key; U.K. inventiveness aids rise of high-tech firms; and these British companies are making some 'colorful' profits

There was great excitement at Instrumental Colour Systems Ltd. late last month. Prime Minister Margaret Thatcher, on the campaign trail, was here honoring a company considered a good example of a successful British high-tech firm - and bringing attention to her own goal of encouraging technological advance in the nation.

Instrumental Colour is the maker of a computerized system for industrial color matching and color quality control.

Traditionally color matching has been carried out by professional colorists, using their own eyes and experience in selecting dyestuffs and pigments. The human eye, scientists say, can distinguish up to 10 million shades of color - an acuity of commercial importance to companies involved in such areas as textiles, printing, food, cosmetics, pharmaceuticals, paints, plastics, automobiles, candles, and so on. Such firms need the ability to accurately repeat the same color as their products go through their factories.

Instrumental Colour produces hardware to do that trick - at around $70,000 for the ''all-singing, all-dancing version,'' as one spokesman put it.

Why pay so much when the eye has such talent?

Because, Mr. Perry explains, the machine can often save its own cost in months. His company is a world leader in this area, with 1,000 customers in 36 countries. Its only major competitor offering ''a good product,'' says Mr. Perry , is Applied Color Systems in Princeton, N.J.

The machine saves money by matching colors more quickly than a professional colorist, who in some instances may take a day or two. This means manufacturers can reduce down time. Further, the equipment analyzes the color. Different colorants react in different ways on different materials according to the kind of light. Mr. Perry has a display of objects that have remarkably varied colors or shades depending on whether the light is natural, tungsten (ordinary light bulb), or fluorescent.

Second, the machine selects the most economic mix of dyes or pigments able to make the match, or a close approximation, under the various kinds of lighting. It can reduce the number of colorants a firm will need to store. All this can save between 10 and 50 percent on colorant costs. One key element in the machineis a powerful computer to handle what Mr. Perry says are the extremely complex mathematical equations used in color technology. Indeed, until the cost of computing power dropped so dramatically over the past decade, color-matching systems were ''very approximate'' and often impractical, he says.

Today Instrumental Color is selling some 120 of its top-of-the-range machines annually. The price has not changed in a decade. So the real price has dropped dramatically, opening up new markets.

The company may go public this autumn. If it does, Mr. Perry expects it to command a price-earnings multiple of 25 times or more - reflecting the 50 percent annual growth rate of the company over the past 10 years.