How do I change the colour of the blue highlighter?

Don’t know the name of it but I’m talking about this


It’s a little difficult to see with my lazy sepia theme, which is exactly why I want to change the colour of it. Additionally it would be nice to have it constantly active for the rem that I’m writing in.

The blue highlight when opening a page is called .flash and has this default style:

.flash {
    box-shadow: rgba(210, 225, 248, 0.35) 1px 2px 9px 5px;
    background-color: rgba(210, 225, 248, 0.35) !important;
}

Highlighting the focused/currently edited rem can be done like this:

#hierarchy-editor .rem-container--focused {
  background-color: rgba(0,100,100,0.1);
}