The colors you choose for your image can have a profound effect, so it's good to experiment with color editing techniques. To enter the color editing mode, press "e" (while you have a picture on the screen). This will bring up a rectangular dotted outline. Using the "page up" and "page down" keys, you can change the size of the outline. Using the mouse, you can change the position of the outline. When you have the size and position you want, press "enter" to bring up the palette.

Now you can change the colors. At the top of the palette window, you will see two colors. One of these is the "selected" color (a color is selected when the cursor is over that color - in the image or in the palette). Beside the selected color (at the top of the palette) are three boxes showing the red, green and blue values for that color. One of these boxes is highlighted, showing that it is the currently selected value. You can change this value by pressing "+" or "-" to increment or decrement (respectively) the selected value by one step. You can also increment/decrement five steps by pressing "page up" or "page down". To change which value (red, green or blue) is selected, press "insert" or "delete".

The other color at the top of the palette is the "active color". You choose the active color by selecting it (see above) and then pressing the space bar. Now you can do something really neat: create a smoothly shaded range of colors. To do this, select a color by putting the cursor over it. Make that color active by pressing the space bar. Now select another color, and press the "=" key. This will cause all colors in the palette between the selected and active colors to change. The result will be a smooth shading from one color to the other.

There are hidden colors in the palette (represented by grey boxes whixh are "xed" out). To see and edit these colors, you must rotate the palette. This can be done by pressing "<" or ">" (they are directional arrows, and will rotate the palette left and right, respectively). Be sure to count how many steps you have rotated the palette, so that you can rotate back after editing the hidden colors. The top left color in the palette is fixed. It does not rotate with the rest of the palette.

Try this: Move the cursor to the edge of the structure you want to show. This causes the editor to select that color. Press the space bar to make it the active color, and then change that color (usually to make it darker and emphasize the boundary). Then do the same with the other side of the structure. Having made one edge color active and the other selcted, press "=". At this point you can select a color between the two edges and make it lighter (add 10 points each to R,G,B - and then maybe more). Then select the lighter color and "=" to each of the edges.