color variable definition

[stefan-korn]

Custom color variables (i. e. primary color) are defined in default.css.

But this does not make use of the Bootstrap sass variables. Why not override the variables in styles.scss like it is already done for some variables?

This way the css variables for :root would be generated automatically, at least for existing Bootstrap variables. And variables that Bootstrap does deviate from each other will be generated automatically too (which is not the case right now), like for example some border colors or text colors that are based on $primary.

And redundancies like defining --primary and --primary-rgb would be avoided.