3 colours Spiced Ginger, Rustic Oak, Evergreen Fern. Brush Tip Watercolour Pens. Nuvo Aqua Flow pens are uniquely designed to create a watercolour effect without the hassle and mess. These highly pigmented water-based pens leave you with a bright, vibrant fish. The perfectly formed watercolour brush nib makes the pens extremely versatile and is perfect for adding small detail or colour washing large areas.