I was informed it is accessible from the developer’s side and has something to do with changing a few parameters on the style.css.
If you need an even higher level of customization, DHIS 2 lets you upload your own CSS files through the Web API. You can inspect the HTML structure and classes of the login page, create your own stylesheet (CSS file) and upload the file through the Web API. - @Lars from Webmasters Stack exchange
Maybe @Stian can advise more on this.
Best,
James.