Hi Haruka,
To be honest I'm not aware of any consumer suppliers for zips that are fairtrade even though there may be some around...Have you thought of using zips from second hand clothes, recycling them? At the end of the day the idea of sustainability is in it's meaning to last long so recycling forms an important part of it...As for colouring, experiment around with plants, the most obvious one being beetroot juice, there is some information to be found online :)