This is the index page to a library of high quality image files representing the aim colors of the OSA Uniform Color Scales. The 424 full step aim colors and the 54 half step colors with integer values are presented as 111 arrays defined by the 9 standard cleavage planes (described below); each color appears 3 or more times within different color arrays. All planes show the full step aim colors as 65 pixel (~16mm) discs in the correct interspacing of colors on the standard 30% reflectance background. The half step colors are shown only in the three **L**, **j** and **g** arrays. This is currently the most accurate and largest format representation of the UCS available online.
The three dimensional UCS color space is defined by the vertical **L+/L–** or *light vs. dark* (lightness) dimension, perpendicular to the horizontal dimensions **j+/j–** or *yellowness vs. blueness,* and **g+/g–** or *greenness vs. redness.* Thus a **j+g+** color will be yellow green and a **j+g–** color will be orange. For this image library, I have inverted the standard orientation of the **g** dimension so that values increase from left to right (negative values are on the left).

The spacing among aim colors is defined across all three dimensions of a perceptual color space by the geometry of the cuboctahedron (diagram, below).

**cuboctahedral geometry of the osa uniform color scales**

lightness is measured on the **L+/L–** dimension, yellow/blue on the **j+/j–** dimension and red/green on the **g+/g–** dimension; rhombohedral stacking of color "atoms" defines a total of seven unique cleavage planes through the color space (labeled on front planes), with additional two cleavage planes (not shown) defined perpendicular to the **j** and **g** dimensions. (**Note**: direction of **g+/g–** dimension is reversed from standard orientation in all image files.)

This rhombohedral solid defines the type of stacking observed in the carbon atoms of a diamond crystal or in the oranges of a fruit stand display. The spacing in all directions is perfectly regular and maximally compact, creating a lattice for color measurement.

The opposing faces or facets of the cuboctahedron define seven **cleavage planes** through the perceptual color space, and joining cuboctahedrons vertically defines two more planes, perpendicular to the **j** and **g** dimensions. The edges of the cuboctahedron define the intersections between two cleavage planes, which form linear *uniform color scales.*

Each cleavage plane contains all the aim colors whose **Ljg** coordinates satisfy one of the following nine formulas:

1. **L** = *constant;* **j,g** take any values

*a plane perpendicular to the ***L** dimension and parallel to the **j** and **g** dimensions, forming a 1:1 square lattice of colors

2. **j** = *constant;* **L,g** take any values

*a plane perpendicular to the ***j** dimension and parallel to the **L** and **g** dimensions, forming a 1:1.4 rectangular lattice of colors

3. **g** = *constant;* **L,j** take any values

*a plane perpendicular to the ***g** dimension and parallel to the **L** and **j** dimensions, forming a 1:1.4 rectangular lattice of colors

4. **L + j** = *constant;* **g** takes any values

*a plane parallel to the ***g** dimension, at 55° to the **j** dimension and 35° to the **L** dimension, forming a 1:1 hexagonal lattice of colors

5. **L – j** = *constant;* **g** takes any values

*a plane parallel to the ***g** dimension, at 55° to the **j** dimension and 35° to the **L** dimension, forming a 1:1 hexagonal lattice of colors

6. **L + g** = *constant;* **j** takes any values

*a plane parallel to the ***j** dimension, at 55° to the **g** dimension and 35° to the **L** dimension, forming a 1:1 hexagonal lattice of colors

7. **L – g** = *constant;* **j** takes any values

*a plane parallel to the ***j** dimension, at 55° to the **g** dimension and 35° to the **L** dimension, forming a 1:1 hexagonal lattice of colors

8. **j + g** = *constant;* **L** takes any values

*a plane parallel to the ***L** dimension, at 45° to the **j** and **g** dimensions, forming a 1.4:1.4 diagonal square lattice of colors

9. **j – g** = *constant;* **L** takes any values

*a plane parallel to the ***L** dimension, at 45° to the **j** and **g** dimensions, forming a 1.4:1.4 diagonal square lattice of colors