Three overlapping semi-transparent red, green, and blue squares form the classic RGB color-mixing diagram, revealing secondary colors where they intersect. The React components `MyRect` and `MyCircle` render SVG rectangles with configurable fill, opacity, and positioning, while D3 v5 supplies the scaling and layout logic in the background. Static SVG shapes are composed in a React component tree, with each square’s blend determined by a fixed opacity value of 0.9.