A simple html element with CSS background linear-gradient.
Goal: Fade background on hover. Does not work (with transition background), see example below - Why?
ui-accordion-header {
  border: 0 none;
    font-size: 100%;
    line-height: 1.3;
    list-style: none outside none;
    margin: 0;
    outline: 0 none;
    padding: 0;
    text-decoration: none;
}
.mx-accordion h1 {
    background: linear-gradient(0deg, rgba(227,227,227,1) 20%, rgba(247,247,247,1) 100%);
    border: 1px solid #e3e3e3;
    border-width: 0 0 1px;
    color: #000;
    padding: 7px 10px;
    margin: 0px;
    
    transition: background .2s ease-in-out;
}
.mx-accordion h1:not(.ui-state-active):hover {
    background: linear-gradient(0deg, #e1ebff 20%, #e1ebff 100%);
    cursor: pointer;
    color: #027BFF;
}<div id="accordion" class="mx-accordion ui-accordion ui-widget ui-helper-reset" role="tablist">
<h1 class="ui-accordion-header ui-corner-top ui-accordion-header-collapsed ui-corner-all ui-state-default ui-accordion-icons" role="tab" id="ui-id-4" aria-controls="my-filters" aria-selected="false" aria-expanded="false" tabindex="-1"><span class="ui-accordion-header-icon ui-icon ui-icon-triangle-1-e"></span>
        <a href="#">My Text</a>
    </h1>
  
  </div> 
     
    