Frontend & browser·Rendering and the browser pipeline
you changed a colour and nothing moved, but the browser still had to redraw those pixels.
Repaint
Also calledpaint, redraw
Filling in the pixels for boxes whose geometry has not changed: colours, backgrounds, shadows, borders, text. It is cheaper than reflow because no positions are recomputed, but it is not free, and a full-page repaint on a complex background still misses frames. Every reflow forces a repaint of what moved; a repaint does not force a reflow, and that asymmetry is the whole reason the distinction is worth knowing.