Color Picker Tool

Sampled (or picked) colors from the Color Picker Tool are stored in the swatch next to the dropper icon on the Color panel.

The following settings can be adjusted from the context toolbar:

Auto-apply—when enabled (default), the picked color will automatically apply to the selected object's Fill or Stroke, depending on which color selector is active on the Color panel. When unselected, the picked color is not automatically applied.
Radius—Choose to sample from directly under the cursor (Point 1x1) or from differently sized square areas where the color is averaged.
Source—determines from where the tool can pick colors. Current Layer restricts picking to the currently selected layer; Global picks from all layers.