Accepted answer

if the times that you have are static strings, you can convert them into a datetime object...

//convert 'string' times into a timestamp (milliseconds)
//so long as your string times are consistently formatted
//e.g. "0:03:00" not "3:00"
var t = date.parse("1-1-1 " + yourtime)

...but if you can turn them into a millisecond value at all, you should be fine.

then use normal time format for the y-axis, and format it as you like using the date label format...

var chart = new highchart({
    yaxis: {
        type: 'datetime', //y-axis will be in milliseconds
        datetimelabelformats: { //force all formats to be hour:minute:second
            second: '%h:%m:%s',
            minute: '%h:%m:%s',
            hour: '%h:%m:%s',
            day: '%h:%m:%s',
            week: '%h:%m:%s',
            month: '%h:%m:%s',
            year: '%h:%m:%s'

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