Branding and colors

[Katrix]

I tried to find any information about what is the "official" colors for the Sponge project. But I couldn't find anything. Expected it to be located here. https://docs.spongepowered.org/stable/en/about/assets.html

Also, maybe add some notes on the usage of the Ore logo?

[stephan-gh]

There are some basic guidelines in the Sponge Branding Manual

[Inscrutable]

... which is planned to become part of the docs, in #470, along with the Art assets.

[Inscrutable]

One day @Mumfrey will make it all official...