Thanks for bringing this up. I have had another look at the dictionary definitions. For coḷa DOP (Margaret Cone’s Dictionary of Pali) say: “cloth; a piece of cloth; a garment”. And for dussa it has “cloth; clothes”. Moreover, it defines dussapaṭṭa and coḷapaṭṭa in exactly the same way as “a strip of cloth”. On top of this the Abhidhānappadīpikā, the Pali-Pali dictionary of the commentaries, defines dussa in terms of coḷa. None of this is very helpful, except for making it clear that the words are synonyms or at the very least near synonyms.
So we need to turn to the commentary, which says: Dussapaṭṭenāti setavatthapaṭṭena … Coḷapaṭṭādīsu coḷakāsāvaṃ coḷanti veditabbaṃ, “a dussapaṭṭa is a white strip of cloth … a coḷapaṭṭa, etc., should be understood as a cloth which is an ocher cloth.”
I don’t find it particularly convincing that dussa must refer to a white cloth, but perhaps there is something to the idea that a coḷa is ocher in colour. I am thinking we might keep fabric for dussa, but render coḷa as “monastic cloth”. I’ll think about it a bit more.
One of the issues with this sort of problem is that we do not know why both dussa and coḷa are given in the text. It is tempting to think they are there because they have different meanings, but that is not necessarily the case. It could be, for instance, that a later editor added one of the two simply to make sure the text was exhaustive. Or it could be that slight variants in dialect or developments in the language after the Buddha passed away made it seem reasonable to use two words to express the same idea.
My impression is that the commentaries often try to find distinctions where it is hard to argue they exist. The commentaries’ position seems to be that the Canonical text is all the word of the Buddha and so every word and expression must be uniquely meaningful. In the present case, however, I doubt it, especially since the dictionaries treat them a synonyms. And DOP is mostly based on the Canonical vocabulary.
I have taken on board @sujato’s admonition not to over-determine the text we are translating, that is, trying to see meaning where in fact there is none. It is prudent to translate the text as it stands, so far as that is possible, without assuming hidden meaning. To sum up, I am reasonably satisfied with leaving the translation as it is, but I shall consider the issue a bit more.
But thanks again for your careful work!