I find new feature after last update

Hello,
I find new feature after last update.
User can change text background.
If I understand right, I can change a colors by css:

#es .es-story-bg-menu-preview.es-story--bg-1 {

    background-image: -webkit-linear-gradient(left,#edf0f5 0,#c6c6e4 100%);

    background-image: -o-linear-gradient(left,#edf0f5 0,#c6c6e4 100%);

    background-image: linear-gradient(to right,#edf0f5 0,#c6c6e4 100%);

    background-repeat: repeat-x;

}

#es .es-story-bg-menu-preview.es-story--bg-2 {

    background-image: -webkit-linear-gradient(left,#f3fbe6 0,#e1e05d 100%);

    background-image: -o-linear-gradient(left,#f3fbe6 0,#e1e05d 100%);

    background-image: linear-gradient(to right,#f3fbe6 0,#e1e05d 100%);

    background-repeat: repeat-x;

}    

#es .es-story-bg-menu-preview.es-story--bg-3 {

    background-image: -webkit-linear-gradient(left,#eafbe1 0,#87e98c 100%);

    background-image: -o-linear-gradient(left,#eafbe1 0,#87e98c 100%);

    background-image: linear-gradient(to right,#eafbe1 0,#87e98c 100%);

    background-repeat: repeat-x;

}}

#es .es-story-bg-menu-preview.es-story--bg-4 {

    background-image: -webkit-linear-gradient(left,#fbe1fe 0,#e69af6 100%);

    background-image: -o-linear-gradient(left,#fbe1fe 0,#e69af6 100%);

    background-image: linear-gradient(to right,#fbe1fe 0,#e69af6 100%);

    background-repeat: repeat-x;

}

#es .es-story-bg-menu-preview.es-story--bg-5 {

    background-image: -webkit-linear-gradient(left,#edf0f5 0,blue 100%);

    background-image: -o-linear-gradient(left,#edf0f5 0,blue 100%);

    background-image: linear-gradient(to right,#edf0f5 0,blue 100%);

    background-repeat: repeat-x;

}

I changed colors , but without result.
If you have tutorial or can explain me how it work.

Regards,
Lazer