In general the background colors in a theme
are either light or dark, but not both.
This allows components to be freely mixed together.
However in some cases you have an area of the page
where the lightness of the background is reversed.
For example on a light page you may have an off canvas (aka drawer)
where the background is dark.
oj-contrast-marker is a marker class
for an area with a contrasting background color.
Using compound selectors some components
know how to render themselves on a contrasting background.
For example the navigationList will render itself
differently when an ancestor has
oj-contrast-marker on it.
Note that the components that support this are very limited.
oj-contrast-marker is only a marker.
It has no css properties, for example it does not set foreground/background colors.
<div class="oj-offcanvas-outer-wrapper oj-offcanvas-page">
<div class="oj-web-applayout-offcanvas oj-contrast-marker oj-offcanvas-start">
<!-- Navigation List -->