This Java applet, which requires the Java Plugin, explores the range of colors by looking at and within the color cube. It begins by depicting one of the six faces of the cube. You can select any face by clicking the buttons on the right.

Each face is 256 pixels on a side, so the cube contains every color in the 24–bit spectrum. As you move the cursor over a face, the hexadecimal number of the color pointed to is shown in the upper right. On the Black-Blue-Red-Magenta face, point to the Black corner, and notice how the color changes from 000000 to 0000FF as you move towards the Blue corner. This is the same Blue axis seen when we began constructing the cube.

Each face represents a range of values on two axes, and a constant value (00 or FF) for the third, which points into the screen. By moving the slider below the cube, you can move along the third axis to reveal layers within the cube below the currently selected face. The number on the slider indicates the number of pixels below the selected face; on the top three buttons this is the same as the color value for the third color, and on the bottom three it is its complement (255 – X).

By clicking on the Web Safe button you can restrict the display to web safe colors. This is a good way to visualize the gamut of colors available in a browser and the relationships between them. You can click on a color to lock the hexadecimal display, then select and copy the number from the display and paste it into an HTML document. Click the cube again to unlock the display.