Is the iron rust found on a worshipper's clothes excused, knowing that its color on the garment is like the color of excrement?

Iron rust is pure (tahir) and not impure (najis), and there is no harm in praying with it on clothes; because the only obligation is to purify clothes from impurities, and there is no consideration for its color resembling the color of excrement. What matters is its true nature, and as long as its substance is pure, its presence on clothes does not cause harm, although washing it for cleanliness and adornment for prayer is better.