Coloring is a fundamental yet time-consuming task in the 2D animation production pipeline. Traditional methods typically rely on frame-by-frame user interaction, leading to high user time and production costs. In this paper, we introduce PropColor, an interactive yet simple tool to propagate colors between adjacent frames of a hand-drawn animation. Starting with an initial frame colored by the user, our method propagates colors to neighboring frames based on the Delaunay triangulations computed from the sketch contours and the color hints. In addition to propagating colouring between frames, our method also associates a confidence score with each of them. This enables to identify the frames where user intervention is needed the most, either to validate the result or to provide additional color hints. Experiments show that our lightweight tool gives real-time feedback and significantly cuts down the animator's time.