Hi

Give me your site URL please so that I can check?

-Regards

/* WHITE OFF-CANVAS X */
.offcanvas-active .burger-icon>span {
    background-color: #ffffff;

/* HAMBURGER FONT SIZE & COLOR */
#offcanvas-toggler span, .icon-bar > span {border-bottom: 4px solid #ffffff;}

Yes, you can ....and those tip all are described in Helix documenation: https://www.joomshaper.com/documentation/helix-framework/helix-ultimate-2/customization-tips

In separate section there are tips also for older Helix Ultimate 1.1.x version.

Thanks @Joe

in your first code "}" is missing. Next time just link our guide.