Iodine solution: dissolved iodine crystal + water
Paint thinner is added. What happens to the iodine?
When iodine is added to an organic solvent, S, there are S:? I2 interactions that give the solutions distinct colors [1,2]:
C2H2n+2, CCl4: violet
aromatic hydrocarbons: pink-red
alcohols, amines: brown
The most common paint thinner  is a aliphatic hydrocarbon fraction from petroleum refining so it would violet with I2. Another paint thinner is toluene, an aromatic hydrocarbon, that would turn pink-red with iodine. A third paint thinner is acetone and although not specifically mentioned in the references is a strongish donor so iodine would turn it brown. (Acetone is miscible with water however.)
The color of iodine in a paint thinner can therefore be used to help identify the solvent.
 F. A. Cotton, G. Wilkinson, et al, Advanced Inorganic Chemistry 6th ed (1999). p 551.
 N. N. Greenwood, A. Earnshaw, Chemistry of the Elements 2nd ed. (1997) p 806-807.