Problem text color when using black color alarm with normal theme and dark theme

[oijkn]

Issue Summary
If I set color alarm to black with normal theme, the text is not readable.
If I set color alarm to white with dark theme, the text is not readable.

Environment

• OS: CentOS 7

• API version: 8.6.4

• Deployment: Docker

• Database: Postgres

• Server config:
  Auth enabled: Yes
  Auth provider: Keycloack
  Customer views: Yes

• web UI version: 8.6.1

• CLI version: 8.6.4

To Reproduce
Steps to reproduce the behavior:

1. Set color alarm to black
2. Click on alerts menu

Expected behavior
A white text over black color

Screenshots

[satterly]

The previous version (in AngularJS) had the following ...

    <tr ng-repeat="alert in alerts | filter:filter | orderBy:predicate:reverse | limitTo:alertLimit"
        ng-style="{ 'color':  colors.severity[alert.severity] == 'black' ? 'white' : colors.text, 'background-color': (bulkAlerts.indexOf(alert.id) > -1) ? colors.highlight : colors.severity[alert.severity] || 'silver' }"
        ng-click="click($event,alert);">

https://github.com/alerta/angular-alerta-webui/blob/4d0b6327cd3bcde44df6a3db9ad961a92e080748/app/partials/alert-list.html#L48-L50