the color change expected to observed is from purple to colorless. initial purple color is from the manganate ions. after potassium iodide is added, it reacts with potassium manganate. the iodide ions are oxidized by manganate ions. the oxidation reaction converts purple manganate ions to colorless manganese ion (II). meanwhile iodide ions are oxidized to iodine. the iodine formed can be observed as brown color.

hence overall color change is purple to colorless (manganate ions (VII) to manganese ions (II)) , and possibly brown (because of iodine).

hope this helps :-)