Hey anons first time posting on this board.
So I need some advice about mixing chemicals, I have a sort of presentation (science themed) and here's the idea:

We 4 test tubes, two of them will be identified as a "problem" while the other two are not (I'm thinking two different colors for identification)

Then the two "problems" (after identifying) will be mixed again with our solutions (two "solutions") to give a final mixture.

Can anyone give me some everyday household chemicals that will give a dramatic effect such as color change and maybe a little smoke. Nothing too flashy though, and guaranteed not to explode or hurt someone.

Thanks a lot!