reaction in which colors change from blue to green,then from green to yellow,then to orange and afterthat blue

Answer 1

This sounds like oxidation of blue Cr2+ to green Cr3+ and then the two forms of Cr6+ (chromate - yellow, and dichromate - orange), and then reduction back to Cr2+.

The first stage may have been using alkaline hydrogen peroxide, followed by acidification and then reduction - perhaps using zinc.

Answer 2

There's another one that's not as sharp as the one you're talking about, but very easy to do.
You take milk of magnesia, or magnesium hydroxide and put it in a beaker with water and a magnetic stir bar. Then add some universal indicator. Then when you add a little bit of strong acid the solution will turn pink, then yellow, then green, and eventually will fade back to purple. It takes like 2 minutes to set up and it's pretty foolproof.