Testing: Color configuration

[jimsafley]

The color-config branch adds the ability for users to configure the color of their diagrams. Every diagram configuration section now includes a "Color fill" setting or a "Color scheme" setting. The "Color fill" setting accepts a hexadecimal color code. The "Color scheme" setting provides a handful of pre-set color schemes from which to choose.

[allanaaa]

Love it. Works great.
If there was a way to improve it, I'd say when you select a colour scheme from the dropdown, we could show the 8-12 colours in a row of blocks below, just the way the help page does. But it's not necessary.