If we're talking WWII I would hazard a guess that on American and British tanks for the most part the extra links would remain in their original color. Seems like most of the sources I have show that relatively few paint schemes were applied in the field, other than the occasional white wash or local scheme. Now Germany would be a different matter IMHO. Tanks came off the assembly line in the base color, and were delivered to the field with tins of undiluted paint as a general rule. Once in the field, dilution of the paint, method of application etc would have varied I would think. Overspray and such on pioneer tools and track spares would have been the rule rather than the exception if I had to guess. I defer to others with more knowledge, but this is what my observations have shown to be trends.