"Looking human through a camera" is a potentially powerful technique to facilitate human-computer interaction. Many 2D/3D visual human tracking techniques have been introduced in area of computer vision, and applied to smart surveillance, motion analysis, interactive computer graphics and virtual reality applications. For applications emphasizing real time interactivity, the visual tracking techniques need to be fast, robust, and preferably run on an inexpensive hardware system. In this paper, we present a relatively inexpensive (e.g. run on a high-end PC) but reasonably robust real time motion-tracking system based on a simple 2D color object segmentation and recognition algorithm. Users grasp color objects for achieving more exact tracking performance on their hands and make predefined motion gestures continuously. Through object segmentation processing based on color information, 2D positions of the objects are computed. And then, a motion gesture corresponding on these 2D position trajectories is found by a simple correlation-based matching algorithm. Also, we demonstrate this system by applying it to a popular interactive entertainment (e.g. TETRIS).