Deseng-53 Site style rebrand

I think this ticket is a great initiative and I'm stoked that it will be going to production. There are a couple of small things here:

* Some colour variables could be given more readable names (that include the colour name)

* Some colours still use hex literals instead of variables

* There is some commented out code that may be intentional, but I left a comment in case it's not

* The colour black is given a variable many times, possibly because this is a retrofit and we want the variables separate in the future. If not, then we should consider consolidating some variables either now or in a future ticket.

Thanks for the thorough review @robrien-bcgov @jareth-whitney.

Since we generally don't block PRs for not using CSS variables, and because this is Steve's code, I won't do the variables piece. The ticket assumes the code is good to go and just needs to be merged
I will remove all the commented out code because it adds nothing(won't be used later, not used as documentation) and increases clutter

bcgov / landuseplanning-public

Deseng-53 Site style rebrand #84