This example demonstrates a utility function that generates random hexadecimal color strings, either light or dark depending on a boolean argument. It shows a simple technique for constraining color brightness by selecting characters only from specific hex ranges—`a` through `f` for light colors and `0` through `5` for dark ones. The function builds a six-character string by repeatedly picking a random index from the appropriate key array using JavaScript’s `Math.random` and `Math.floor`. No external libraries are used; the code relies solely on native JavaScript string concatenation and array indexing to produce the final color value.