Function clock_highlight_color 

fn clock_highlight_color(
    clock_idx: usize,
    single_active_clock: bool,
    fallback_color: Color32,
    color_list: &[Color32],
) -> Color32

Selects a stable highlight color for a clock index.

If only one clock is active, the base fallback color is always used. For multi-clock rendering, the color cycle is: fallback, then color_list entries.