I'm trying to make it by this code:
var $li = $('#marks').find('li[data-id=111222333]'),
color = 'rgb(' + $li.css('background-color').match(/\d+/g).map(function (i) {
return (+i > 100 ? ((+i + 33) > 255 ? i : +i + 33) : +i + 99);
}).join(',') + ')',
gradient = 'repeating-linear-gradient(45deg, '+$li.css('background-color')+', '+$li.css('background-color')+' 3%, '+color+' 3%, '+color+' 6%);';
$li.css({'background-image': gradient});
But it doesn't works... I'm also trying this:
$li.css({'background': gradient});
$li.css('background', gradient);
$li.css('background-image', gradient);
$li[0].style.background = gradient;
$li[0].style.backgroundImage = gradient;
Butt result is same... Any ideas?!
UPD. Try here https://jsfiddle.net/kk77x3ru/
$li.css({background: gradient});? Can you check the value in console?