From left to right, aqueous solutions of: cobalt(II) nitrate; potassium dichromate; potassium chromate; nickel(II) chloride; copper(II) sulfate; potassium permanganate.
Pretty! These are transition metals solutions, but rare earth elements are also known for producing brightly colored solutions. This image is public domain and can be printed, saved, and used. Be sure to give credit to Ben Mills!