It is no longer possible to easily insert text of an arbitrary colour in the new Confluence 4 editor

In the old wiki markup editor, it was easy to insert text using all the colours of the rainbow! (using the {color} macro).

These days, users are restricted to only being able to easily use colours that are available in the colour picker in the editor toolbar. If you want to use a different colour, you have to use the insert wiki markup dialog.

It would be great if there was a way to easily select other colours. This could be accomplished, for example, by allowing a user or administrator to customise the colours that appear in the picker, or adding an option to the picker that allows an arbitrary colour choice to be typed in.

This was raised by a customer on answers.atlassian.com: https://answers.atlassian.com/questions/35516/how-do-i-revert-to-the-default-text-color-in-the-confluence-4-x-editor