app/webpack/stylesheets/components/_notification_banner.scss
// stylelint-disable declaration-no-important
.govuk-notification-banner--alert,
.govuk-notification-banner--error {
border-color: $govuk-error-colour !important;
background-color: $govuk-error-colour !important;
.govuk-notification-banner__link {
@include govuk-link-style-error;
}
}
.govuk-notification-banner--notice {
border-color: $govuk-success-colour !important;
background-color: $govuk-success-colour !important;
.govuk-notification-banner__link {
@include govuk-link-style-success;
}
}