Hard-edged, flat, and without a trace of the artist's hand, Kelly's signature imagery is nonetheless based on architectural and natural forms. In Kelly's hands, abstraction becomes a conceptual method by which he reconfigures and recontextualizes the forms and structures of the real world. His paintings and sculptures represent a subjective interpretation of reality, rather than a descriptive copy of it. In "Blue Green Red," he has juxtaposed three bold colors in a highly skillful and effective manner to create a complex picture in which color and shape are one. The edges of one shape—the rectangle—are identified with the edges of the canvas, while the blue ellipse expands beyond the canvas, forcing us to finish it in our minds. Despite the clean, precise rendering of the ellipse, its form is irregular and seems to float and swell, activating the entire composition.
Kelly's arrangement of the complementary colors, which work to intensify one another at their intersections, is also an essential component of the work. The opposite colors of red and green both add to the boldness of the work and divide the overall rectangle into distinct units. The artist has also exploited the tendency of warm colors to appear to come forward on the picture plane, and cool ones to recede. While the bright, unmodulated colors are unequivocally two-dimensional, we can nevertheless read the red strip at the bottom as foreground and the cool green and blue as receding background. When viewed as foreground and background in this way, the sources in nature for Kelly's forms are suggested. Blue and green are the colors of water and earth—perhaps lake and field, as indicated not only by hue but by the swelling, fluid shape of the ellipse and the flatness of the green surrounding it. While the painting itself is continuous with the European biomorphic tradition, its scale is that of the huge close-ups of billboards and movie screens—a very American form.