Dear all,
i am using radzen sidebar like from the CRM Demo. Is there any way to change the background color for the complete menu ?
Ive changed in the styles.css (only for sidebar):
example:
.rz-sidebar {
background-color:red
}
and
.panel-menu{
background-color:red
}
nothing worked 
The following CSS should work:
.panel-menu {
background-color: red;
}
.panel-menu .navigation-menu .navigation-item-wrapper {
background-color: red;
}
Make sure your CSS is included after the theme CSS file. Otherwise you have to use higher CSS specificity or the !important modifier.
many Thanks ! It works, now.
Only sizable Grid columns for the user would be awesome if this could added to the component 
How can i change the panel menu active item colour? I have looked in the css file but there are quite a few items!
In such cases the Browser developer tools always help.
The CSS selector you need is:
.panel-menu .navigation-item-wrapper-active:before {
}
Good Job!
"give a man a fish and you feed him for a day ; teach a man t o fish and you feed him for a lifetime." 
Another thing to not become mad .............
.rz-panel-menu .rz-navigation-item-wrapper-active::before {
content: none !Important;
}
To remove the space of before pseudo-class add {content:none} , !Important to ovverride base stylesheet