The Memory box let you store some colors, and reused them later to generate an HTML file, to send them by mail, or to apply them to a HTML template.
You can add a color to memory each time a white upper-left corner is displayed in a colored rectangle, anywhere in the colordb window:
When your mouse is over this corner, the mouse cursor changes to a cross, so you know you are on the "add to memory" part of the sample (if you click somewhere else in the colored square, it is not brought to memory but selected as the new current color).
Note you can not add to memory twice the same color.
To remove a color from memory, note that the upper left corner is not white but dark gray:
Click on it to remove the color from memory.