We introduce Ciallo, an open-source next-generation vector paint program, which supports GPU-rendered stylized strokes and real-time bucket (region) fill. All strokes and fill regions are represented in editable polyline vector format instead of in raster format. Our novel stroke rendering methods are simple to implement and can potentially replicate the vast majority of brushes in other paint programs. The novel bucket fill can automate parts of the Japanese anime coloring process. In summary, Ciallo presents a new technical paradigm for the fundamentals of 2D digital art production.