You can change the current color using the Color Wheel panel. Most of the panel is occupied by a spectral color ring that allows you to easily fine-tune color settings and select perfect color combinations.
Adjust the color using one of the color markers. The number and position of markers can be adjusted using 5 large round buttons at the top of the panel.
The central part of the color wheel is a triangular or square field. Move the small round marker vertically to adjust the brightness of the selected color or horizontally to adjust its saturation. You can select the shape of the field using the / buttons.
The selected color is displayed in the square box on the left-top corner of the panel. Double-click on it to open the color selection dialog.
Alternatively, you can pick colors using the Eyedropper tool located at the top of the panel.