Colour in muriate of Potash?
If you have seen pink salt crystals from Khewra mines in Pakistan (the so-called Himalayan pink salt) sold at exorbitant rates in grocery stores, you would find out it is nothing but NaCl with a small amount of iron oxides as stated above. If you dissolve large tablespoons of such salt crystals in water, you will see a brownish precipitate sitting at the bottom on the container.

The word muriate reminded me of ancient chemistry books of the 1940s. It is a very very old name for a salt of hydrochloric acid.