color: move triggering of the initialisation logic in core
We now run the color initialisation as part of the standard dispatch. This is
opening the way for multiple cleanups since we now have access to the multiple 'ui'
object and we'll be able to see difference between global and local config. This
cleanup will arrive in later changesets.
As a side effect, the '--color' flag is now working without the extension.
Since we now properly initialize color for each ui idependently, we get a
warning message twice.