Low contrast on main page

[edent]

The current text colour is rgb(50, 198, 176). I think that's caused by this line setting the teal colour
https://github.com/sustainers/website/blob/master/_sass/_variables.scss#L3

I think the colour should be set to the (appropriately named) $teal-dark-wcag: #128273; on

https://github.com/sustainers/website/blob/master/_sass/components/_header-hero.scss#L38

There are a few other places where this needs to be changed. But I'll send a PR for this one first to make sure I don't break anything :-)