JOHNSON CITY, Tenn. (AP) _ At least once a week, from his vantage point atop Clinch Mountain, Francis Collins files an intelligence report of sorts.

He calls state officials to tell them just how red, yellow and gold the forests below his restaurant are becoming.

Collins is one of a small band of ''color observers'' who will alert the rest of North Carolina, Kentucky and Tennessee when fall color is at its peak.

Spectacular foliage may be most closely associated with New England - an estimated 3 million ''leaf peepers'' from across the country visit that region each fall - but it also brings thousands to the southern Appalachians.

The three Southern states have formed a loose network of color watchers to help tourists plan their trips.

Many of the observers are forestry or recreation officials. Some, like Collins, are volunteers - regular folk with time on their hands and an eye for color: the reddish-orange of the sugar maple, the solid, fiery red of the sweet gum tree, the yellows of the elm, hackberry and tulip poplar, and the splash of green of the fir.

Some watch from their front porches, others from their cars and trucks as they drive through the forests on these warm September days and cool evenings.

''As long as I've lived around these hills, you can pretty well guess at it,'' Collins said. ''We're setting right up on top and we can pretty much see the world.''

And the way things are shaping up, now the peak will be the third week of October, Collins said. He guessed now that maybe 15 percent of the leaves have changed on the mountaintop. In lower elevations, a few leaves are turning now.

Admittedly, ''there's not a real scientific sample,'' said Bob Miller, spokesman for the Great Smoky Mountains National Park. Park officials look at the trees each week from late September to early November to estimate a percentage.

Collins has read up on his trees and keeps a close eye on the subtle changes. In a pinch, he can seek some advice from some of the old-timers who come by.

Most people helping the state simply know trees.

''The only way I've got to go is the degree of color,'' said James Smith of Rockwood, a grocery-store owner and color observer last year. ''I was raised in the country so I know most of the trees.''

Smith and Collins agreed 1990 has the makings of a good year for color. The summer was hot, there was rain late in the season and fall has arrived with warm days and cool nights.

''It looks like we're going to have a good change,'' Collins said.