This script modifies the colors available to the in-browser Desmos graphing calculator.

desmos_color_modifier.js

(function() {
    // Calc will be defined when on desmos.
    let expressions = Calc.getExpressions();
    if (expressions.length == 1 && expressions[0].latex == "") {
        Calc.removeExpressions(expressions); // this deletes the first expression, because it will already be loaded with the old colors
    }

    Calc.updateSettings({"colors": {
        "RED": "#ff0000",
        "GREEN": "#00ff00",
        "BLUE": "#0000ff",
        "BLACK": "#000000",
        "ORANGE": "#ff8800",
        "YELLOW": "#ffff00",
        "LIGHTBLUE": "#8888ff",
        "PURPLE": "#aa00ff",
        "PINK": "#ff00bb",
        "BROWN": "#D2691E",
    }}); // This defines a new list of ten colors
})();