Chemical reaction for the flow color change from blue to red and again to blue

I am trying to demonstrate color change in the liquid as it passes through a channel to demonstrate blood getting purified after passing through certain organs of the body.


I want the initial color of the liquid to be blue in color and as it passes and comes out of a small pipe, it should change into red color and again after going through a small pipe, I want it to change back into blue color.


In short, blue to red to blue.


I have tried to search things online and I found the following. There is a reaction which involves sodium hydroxide and sucrose. Under stirring upon addition of $\ce{KMnO4}$ the color change happens. But I am not quite sure if I will be able to handle stirring.


So, I am looking for something simpler than that. I am really not that sure if such a reaction exists.


