Multi slider colour question

Like this? jspainter, once you know how to do the mgraphics drawing things. Maybe this will get you started down that (pretty useful!) rabbit hole.

/*
multislider_peakingcolor_example.js

jspainter file adapted for a Forum inquiry.

Author: Tyler Mazaika. 2022-09-15

----------------------------------------------------

When a slider is at the max level, it will draw using the "peakcolor" color rather than the "slidercolor".
*/

if ( this.box.maxclass != "multislider" ) {
    // Alert user if they're using a jspainter somewhere they shouldn't.
    throw new TypeError("multislider_peakingcolor_example.js should only be used with multislider objects.")
}

function paint() {

    var values = box.getvalueof()

    with (mgraphics) {
        // Fill the background
        set_source_rgba( box.getattr("bgcolor") )
        rectangle( 0, 0, mgraphics.size[0], mgraphics.size[1] )
        fill()

        set_line_width( box.getattr("thickness")+0.5 )
        set_source_rgba( box.getattr("slidercolor") )
        var width = mgraphics.size[0]
        var height = mgraphics.size[1]
        var stepsize = width / values.length
        var x = 0
        var y = 0
        var range = box.getattr("setminmax")
        var yfactor = height/(range[1]-range[0])
        var ghostbar = box.getattr("ghostbar") / 100.

        // Establish the y coordinate of zero value. Useful for signed/bipolar drawing.
        var zero_y = (range[1]-0)*yfactor

        // Bar width. Refactored to avoid repeat calculation in the loop.
        var bar_width = stepsize-box.getattr("spacing")

        for (var i = 0; i < values.length; i++) {
            y = (range[1]-values[i])*yfactor

            if ( values[i] == range[1] ) {
                // Value is a Max, so use peakcolor.
                set_source_rgba( box.getattr("peakcolor") )
            } else {
                set_source_rgba( box.getattr("slidercolor") )
            }

            if ( box.getattr("signed") ) {
                if ( y<zero_y ) {
                    // positive value
                    rectangle(x, y, bar_width, zero_y-y)
                } else {
                    // negative value (since y is drawing coordinate, not value)
                    rectangle(x, zero_y, bar_width, y-zero_y)
                }
            } else {
                rectangle(x, y, bar_width, height-y)
            }
            fill()
            x += stepsize
        }
    }
}