align color definitions

- a few of them weren't really defined correctly across gui/cterm
- using color names for cterm is unreliable; better to use codes
reorder uichrome based on `:help hitest.vim`
Visual, VisualNOS, fix blues & add light grey

I had the alignments of blue/dark blue/light blue wrong :/
Converted easy UI Chrome colors to variables

Mostly greys, but some yellow as well.