Comment 5 for bug 1897805

Fwiw, I have this notes for myself. The key is to inherit the default theme instead of Ubuntu theme so everything can be way simpler.

.
└── static
    ├── horizon
    │ └── components
    │ └── _selects.scss
    ├── img
    │ ├── favicon.ico
    │ ├── logo-splash.svg
    │ └── logo.svg
    ├── _styles.scss
    └── _variables.scss

[_variables.scss]

$brand-primary: #772953; // the key brand color

$navbar-default-bg: $brand-primary;
$navbar-default-link-hover-bg: darken($navbar-default-bg, 15%);
$navbar-default-color: #fff;
$navbar-default-toggle-hover-bg: darken($navbar-default-bg, 10%);
$navbar-default-toggle-icon-bar-bg: #fff;

@import "/themes/default/variables";
====

tar -cvzf custom-theme.tgz -C custom-theme/ .
juju config openstack-dashboard default-theme=custom
juju config openstack-dashboard ubuntu-theme=no
juju attach-resource openstack-dashboard theme=./custom-theme.tgz

# off and on is required when uploading a new revision
juju config openstack-dashboard custom-theme=false
juju config openstack-dashboard custom-theme=true