A light string includes a controller and a plurality of colorful light beads. The controller is electrically connected with the light beads and an AC electric supply, and the light beads are connected in series. Two voltage supply lines power the light beads, and control signals from the controller are fused with the power signal and passed to the light beads via the negative pole. The control signal is recognized by each light bead and also passed to the next light bead in the series, to produce a change in the output of each light bead (e.g., color, flashing pattern, etc.). The light beads include three LEDs of different color and can produce seven different colors. Multiple light segments can be connected and controlled by the same controller. The light string design is simple, yet versatile, offering many illumination outputs selectable by a user.