Poppy Red. A pure sienna, mixed from four paints: Cadmium Yellow, Quinacridone Magenta, Ultramarine Blue and Cadmium Red.
Drag a bar to change how much of that paint goes in, and watch the colour change at the top.
Parts are a ratio: a drop, a spoonful, whatever suits the amount you need.
The library and every recipe here are mixed from just these.