Color customization
Color customization can be performed by editing htlm in respective partials (.hbs files usually located in the "ui-bundle\partials" folder path.)
A reference of more customizations can be found here: https://www.w3schools.com/html/html_styles.asp
An example of a line added to the "article.hbs" file:
<article class="doc">
<body style="color:gray;background-color:powderblue;"> (1)
{{#with page.title}}
<h1 class="page">{{{this}}}</h1>
{{/with}}
{{{page.contents}}}
{{> pagination}}
</article>
1 | On this line a custom color has been assigned to the article class, and is why this appears in a webrowser with a non-standard background color. |