Colors

[swagween]

Add a small Color struct to create a palette for the game using bave::Rgba. Colors should include:

sp_black_v{0x231d2aff};
sp_milk_v{0xe5cdaeff};
sp_grey_v{0x535151ff};
sp_mocha_v{0x6f5a48ff};
sp_ice_v{0xd6dbe1e1};

To be changed and others to be added as needed. Should be accessible pretty much everywhere.

[karnkaul]

Some upgrades:

1. It should be data driven: this will allow theming and modding. In code it could be a map of string => Rgba.
2. We should add this to the existing Styles service.