Finex Indicator is typically a gel type strong acid cati­on exchanger.

During the manufacturing process, the resin is injected with a special indicator dye which reacts to the acidity within the beads. Therefore, the resin in hydrogen form will exhibit a purple colour indicating a local acidic environment. When the resin is exhausted, the local bead acidity decreases and the indicator signals the resulting “pH rise” by a colour change from purple to yellow.
The indicator dye used is very resistant against wash-out. The resin is delivered freshly regenerated and washed for optimal performance. This resin is designed for water quality control applications in power plants and comparable facilities.  

Also anion and mixed bed indicator resins are available.