Think of intensely colored geometric abstractions from the 1960s, and you’ll probably picture a Frank Stella or a Kenneth Noland. Less visible today is the work of Larry Zox, a rising star in the 1960s and ’70s whose eye-catching, hard-edged abstractions were snatched up by major museums around the country.

Mr. Zox had a solo exhibition at the Whitney Museum in 1973, but his career trajectory slowed as he shifted toward softer, more lyrical forms. Not having the aggressive support of critic Clement Greenberg or MoMA director William Rubin – boosters for Messrs. Noland and Stella, respectively – may also have been a factor.

Mr. Zox’s current show at Stephen Haller Gallery marks the artist’s second solo exhibition there after a 20-year hiatus from New York. The 11 works include eight paintings and collages dating from 1970 or before, with the rest reflecting his later, looser style.

Mr. Zox apparently found adventure enough within the rectangular format, never straying to the shaped canvases that engaged some of his contemporaries. Indeed, to a greater extent than either Mr. Stella or Mr. Noland, the artist explored how off-balance designs can make specific demands on the colors within.

The raw tones and technique of two early collages from 1962 suggest the lingering impact of Abstract Expressionism. Despite their rough facture – they consist of sections of dark and light paper torn and stapled to a board – both works show a deliberate, tense balancing of blunt verticals and horizontals.

“White Rotation” (1963) explores similar rhythms but in a wholly different style. Colors have brightened, shapes turned seamlessly crisp. This 2-foot-wide canvas is dainty in size but willful in its design; bars of pink and yellow divide its interior space into concise, measured intervals.

The large canvas “Norton Sound, Diamond Drill Series” (1967) shows Mr. Zox at full,splashy speed.Pale lines (actually exposed portions of raw canvas) ricochet about the left half of the canvas, sectioning it into brightly colored diamonds and triangles. One angular, dense, blue-green shape stretches the canvas’s height, just touching its top and bottom edges. To the right, a large, uniformly gray plane holds as a kind of background; a small wedge of subdued orange, desaturated to almost the same visual weight, braces on the left. Stacked totem pole-like atop the green, a triangle of full-tilt orange presides, its contours amplifying the angles below.

The painting brims with arguments about symmetry and its violations. But the elemental exuberance of its colors defies categorization, their footloose energy competing intriguingly with the deliberateness of the design.

Two canvases from the “Gemini” series, both completed in 1970, suggest the artist’s interest shifted from lateral tensions to depths. These wellknown images of four pointed stars ringed by flat, edge-hugging triangles take their life solely from color. In the smaller of the two canvases, the pe ripheral triangles – painted in rich orange; heavy gray; deep, acidic yellow, and shimmering, metallic blue – press upon the center’s stolid green. The relatively even-handed pattern imparts a kind of studied gorgeousness.

There are no works here from the 1970s or ’80s to flesh out the artist’s evolving style. But two recent paintings show his later, more fluid approach. Though its forms are more organic, the huge “Raratin” (2002) has no less vigor than work from the 1960s. Tall, slightly tilting blocks of mild pink, throbbing yellow, and glowing red-orange alternate with cooler, grayer hues to pace out its 10-foot width.These vertical swaths are contained at top and bottom by opposing tidbits of color, imparting a lively variation of scale and turning the whole canvas into an expansive measuring of width and height. The second painting (c. 2000), about a quarter the size, achieves the same luminous breadth in a renewed march of free-form verticals.

Viewing these works down the wall from Mr. Zox’s early geometric images, one wonders: Did his color, so animated since the 1960s, lead to the liberation of his drawing? The good news is that his rigorous attack was always more than just a style, and his forms and colors still know what to do.

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“American Modernism on Paper”is a modest installation of 12 works tucked away in Michael Rosenfeld’s smaller room. The show gives a taste of the fascinating variety of temperaments that shaped American Modernism.

Theodoros Stamos’s large gouache “Cyclops” (1947) uses classic Surrealist biomorphism to good effect, capturing with distended purples and grays the impression (if not the logical attributes) of a rearing one-eyed beast. The wrinkled, brown paper support for a Morris Graves gouache and watercolor, “Message” (c. 1940), neatly rhymes with its description of two dried leaves, one delicately cupping a small dead bird. On another wall, finely spattered and mottled textures enliven Balcomb Greene’s austere, untitled abstraction (c. 1938) in gouache, ink, and tempera.

Most surprising is William Zorach’s watercolor, “Half-Dome, Yosemite” (1920). A picturesque tourist stop would seem like an unpromising motif, but the artist’s purple and sienna washes size up vast spaces and masses with unaffected aplomb; in the foreground a tree, poignant in its craggy loneness, echoes the peak’s vertical face.

Also included in the show are representative watercolors or gouaches by Arthur Dove, Max Weber, William Baziotes, and Oscar Bluemner.

Zox until May 16 (542 W. 26th Street, between Tenth and Eleventh Avenues, 212-741-7777). Prices: $10,000-$160,000. “American Modernism” until May 13 (24 W. 57th Street, between Fifth and Sixth Avenues, 212-247-0082). Prices: $18,000-$110,000.