Those paintings were very big solid areas of blues or greens against reds, complementary colors of full intensity. This time [i.e. 1971-72] what I'm doing is working in ranges and the areas are not large. In other words, they're composed of many lines so that there are no really very large solid areas. So that creates a softness in itself. But the range I work in is a sort of neighbor range or a spectral range where I put a green next to a blue and a blue next to a purple, and a purple next to a red purple and a red purple next to a red, so I've separated the red by three neighbors and you work your way up to that red... The total image is much softer than the very stark image l had in the beginning.⁷¹

In the same year, 1972, Anuszkiewicz was engaged by the Public Art Fund of New York City to design a mural for a windowless exterior wall, several stories high, of the YWCA building in midtown Manhattan. His Portal was one of the most successful works in the City Walls program. Rather than imitate architecture or represent something unrelated to its surroundings, the giant mural unlocked the severe brick wall with a yellow and green gateway, a hundred feet high by sixty feet wide, that suggested a scintillating inner space.

By the mid 70s, the Janis Gallery was specializing in photo-realism, representing Richard Estes, most notably. Anuszkiewiczs decade with the gallery closed with his representation in the anniversary show, 25 Years of Janis, Part 2: From Pollock to Pop, Op and Sharp-Focus Realism. He transferred to the Andrew Crispo Gallery where his first solo show opened in March of 1975.

Three Series — Spectrals, Centered Squares and Temples: 1975-1986

Anuszkiewicz's involvement with mathematics reached its most explicit form in the mid-70s, beginning with the Spectral series. Fields of color, the most extensive in his career to date, are pierced by lines graduated by length and spacing into eighths. These ruler-like markings generate the color shifts called 'simultaneous contrasts' when a warm tone is surrounded by a cool one, or vice versa. Anuszkiewicz used the same kind of markings as borders in Stimulus, 1965, and Intensity, 1965. The Spectral compositions have been aptly described as warm and cool paintings that are "continually monitoring their own temperature."⁷² In Trans Midnight Spectra, 1975, the graduated scales stand upright like blue and green sentinels dissolving into the dark purple background. The result is frankly romantic in a Rothko way. For the most part, on the other hand, the Spectrals pursue the Portals' interest in lighter, 'sunnier' values of yellow and green, admitting even an occasional hint of pink.

The "Spectral Complementaries" constitute a series within the series, numbered with Roman numerals. "This was the first time Anuszkiewicz had created works with so much field color. Perhaps of greater significance was the change from a closed composition to an open format, in which the field of color flows off the canvas."⁷³ In Sunrise Chroma, 1974, which happens to be the last plate in Karl Lunde's impressive monograph of 1976, the red segments of the vertical scales resemble mercury readings in a thermometer.

In retrospect. the Portals and Spectrals of the early seventies represented a lyrical interlude bracketed by the heroic gestures of the sixties and eighties. In retrospect, their soft edges and delicate tints signalled a period of refreshment, and gathering of energies, in preparation for what was to come. As the decade closed, Anuszkiewicz's 1979 show at Alex Rosenberg Gallery was hailed by John Gruen for its "reversion to a simplicity of composition that lends particular impact to a shape with which Anuszkiewicz had long been involved: the centered square. The durability of this image and the subtle coloristic variance within it that continue to produce that sense of timelessness and confirm that Anuszkiewicz is not merely a master craftsman, but also an artist of utmost expressiveness..."⁷⁴

At one point, back in the late 1960s, Anuszkiewicz had almost titled his square within square paintings, Homage to Albers.