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The challenge's like this. Suppose you have a beaker containing a liquid of transparent or any color. You add some drops of another liquid and the beaker turns into, say, red after some swishing. You add some amount of yet another liquid and the solution now turns into cyan. The process is repeated for at least 5 times, giving us a 'chameleon' beaker that eventually displays all the rainbow's colors.

Let's call that a pathway, for I don't know a better word. So... do pathways like that exist? Provided:

  • You can do as many steps as needed. Having way more than 7 colors is even more fun!
  • At each step, the added liquid, the beaker's solution and the result should not share the same color. For example, if we add some blue drops to a transparent solution and it turns blue, then the thing is not really impressive. Adding some purple drops and turning a whole beaker of orange into purple is somewhat OK.
  • Precipitation is acceptable but not encouraged.
  • Dramatic effects like smoke or sizzling are great! If they're not dangerous.
  • The 'added thing' can be liquid or solid or really, any substance.
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    $\begingroup$ Did you consider using Reichardt's dye? $\endgroup$
    – Loong
    Oct 15 at 9:23
  • $\begingroup$ That's the 1st time I heard of the thing, thanks! Could you demo a particular pathway? $\endgroup$
    – longtry
    Oct 16 at 4:28
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    $\begingroup$ You might want to check An Easy and Versatile Experiment to Demonstrate Solvent Polarity Using Solvatochromic Dyes. For example, adding water to a solution of the dye in acetone shifts the colour from green to blue to violet to purple. $\endgroup$
    – Loong
    Oct 16 at 8:07
  • $\begingroup$ Red cabbage "soup" is an indicator that covers abut the whole visible spectrum. It has the advantages of being cheap, safe, and can even be prepared at home. Though in genera( it's not a good idea to eat in a lab, the indicator itself is potable. $\endgroup$ Oct 17 at 2:57
  • $\begingroup$ @Loong unfortunately I don't have access to that article. $\endgroup$
    – longtry
    Oct 17 at 5:01

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