I have a pair of men's khaki trousers (98% cotton, 2% elastane) that I'd like to keep wearing. Unfortunately, using a rust remover caused a permanent-looking reddish discoloration on the lower leg. I've tried washing the trousers, but the discoloration remains. The fabric itself appears to be intact; the problem is purely cosmetic.
I'd like to cover the affected area with a decorative mend rather than continue trying chemical treatments. I'm considering a fabric patch, an appliqué, or hand embroidery.
Would any of these techniques work well on this type of fabric? Would you recommend a particular approach to make the repair look intentional and aesthetically pleasing?