modify css, ideally change menu colors but other colors as well.

[vinceyoumans]

I like this theme but frustrated with all of the theme modifications just to change css.
I am doing a mod get for the theme.
then I have a static/css/main.css that I use to over ride the module get theme.
I added :

:root {
  --red: #b00;
  --blue: #00b;
  --fullwidth: 100%;
  /* --menuBackGround: #8a3535; */
  /* --menuBackGround: #8a3535; */
  --menuBackGround: #7b4242;
  --menuText: #e9dfdf;
  --MenuTextRollOver: #0085a1;
}

then changed all the menu Backgrounds from standard off white to:
stuff like this:

/* --- Navbar --- */
/* menuBackGround */
.navbar-custom {
  background: var(--menuBackGround);
  border-bottom: 1px solid #EAEAEA;
  font-family: 'Open Sans', 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

The method works briefly while using localhost, but after a menu click reverts back to original white.
Not sure the reason why.

But it would be a very nice feature if there was a stock override CSS file where we can modify just colors and fonts.

Perhaps this already exists?