ShadowFox/css/userContent-files/webextension-tweaks/momentum.css

/*! Alters the webextension Momentum
  IMPORTANT: change the Internal UUID */
@-moz-document url-prefix("moz-extension://momentum@momentumdash.com/dashboard.html") {
  body {
    background-color: var(--tone-8)!important
  }
}