A good place to start is to read the attached booklets - pdf files at the bottom of the page - from Blakes and International. Remember Skippers Sintolin can be colour matched to any colour you want.
There are a number available on the net. Below are the addresses.
InternationalsNarrowboats Guide and the Veneziani Paint Guide are available as PDF files and are the attachments at the bottom ...
Vitually every manufacturer has a paint scheme. Below in detail is Blakes - see also our list of downloadable guides for further suggestions. If you are back to 'bright' I would look at the two pack...