theme Hueman

1) I need to change background color of right sidebar
change this css

.col-3cm .main {
  background: rgba(0, 0, 0, 0) url("../img/sidebar/s-right-s2.png") repeat-y scroll right 0;
}

2) You may also like for need find this text on your theme files

2) Solved

1) where can I find this css? Kind of beginner, sorry

wp-content/themes/hueman/assets/front/css/main.min.css

find .col-3cm .main

Do not edit the theme itself. First create a child theme for your changes. Or install a custom CSS plugin.