NOVELTY - An ion exchange resin comprises exchangeable groups (at least 15%) comprising colorant containing at least one of an ion, Lewis acid, or Lewis base. The colorant has a pKa, or pKb of greater than 5 in an aqueous solution at 25degreesC.    USE - In heat transfer system used in fuel cell system and in assembly powdered by an alternative power source; for maintaining conductivity of less than 10 muS/cm in a colored heat transfer fluid (all claimed).    ADVANTAGE - The colorant is free of functional groups that will form an ionic species due to hydrolysis in an aqueous alcohol solution; free of functional groups selected from carboxylate groups, sulfonate groups, phosphonate groups, quaternary amines, groups that carry a positive charge and groups that carry a negative charge. The ion exchange resin maintains conductivity of less than 10 muS/cm in a colored heat transfer fluid; capable of removing ionic species from a treatment solution or heat transfer fluid, maintaining low conductivity in a colored heat transfer fluid and providing color to a colored heat transfer fluid; capable of simultaneously removing ionic species from a heat transfer fluid, maintaining low conductivity in a colored heat transfer fluid and providing color to a colored heat transfer fluid.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) a heat transfer system comprises a circulation loop defining a flow path for a colored heat transfer fluid having a conductivity of less than 10 muS/cm and ion exchange resin comprising exchangeable groups (at least 15%) comprising colorant positioned in the flow path;    (2) a fuel cell system comprises at least one fuel cell containing an anode, cathode, and electrolyte; and a fuel cell heat transfer system in thermal communication with the fuel cell containing the heat transfer system;    (3) a method of maintaining a conductivity of less than 10 muS/cm in a colored heat transfer fluid involves: passing a colored heat transfer fluid through the heat transfer system; and    (4) an assembly powdered by an alternative powder source comprises an alternative powder source and heat transfer system in thermal communication with the alternative powder source (where the heat transfer system comprises circulation loop defining a flow path for a heat transfer fluid having a conductivity of less than 200 muS/cm and the ion exchange resin positioned in the flow path).