You might try some of the websites and organizations devoted to loyalist units in particular, such as royalprovincial dot com. I notice there is some overlap with units such as Lord Dunmore's Ethiopian Regiment so dress may well have carried over from one organization to another. There are some references in secondary sources to the men wearing sashes with the words, "Liberty to Slaves" on them, or painted or embroidered on hunting shirts, etc., but I do not know what support there is for that in primary sources.
You might also try the index for the company journals to see if anything has been published there.
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