Monochrome is a value scale of a single color, ranging from light to dark. Imagine 9 different values of a color. 1 is the lightest, 9 is the darkest, and 5 is midway between. The other values are evenly spaced to show a progression from light to dark. Value 5 is the pure color, values 1 - 4 are tints (by adding white), and values 6 - 9 are shades (by adding black).
This blue bundle has values 1, 2, and 3 and comes to you from Robert Kaufman, including 3 fat quarters of Kona Cotton Solids: