mobile version of the site / menu / stripes

On the mobile version of the site:
How to make the three horizontal stripes of the main menu brighter (in the upper right corner)

It's icon and you can brighten it by changing its color.

You can try to use this custom CSS:

.jub-block .navbar-toggle .icon-bar {
    background-color: #ffffff !important;
}

and change to the color as you wish.