Isaac Newton

That a rainbow has seven colors — 'ROYGBIV' — was Isaac Newton's choice. He first saw five in the prism's spectrum, but believing colors should number seven like a scale, he added orange and indigo. Indigo is the most disputed band today.

Isaac Newton lost most of his fortune in the 1720 South Sea bubble. He famously said, "I can calculate the motion of heavenly bodies, but not the madness of people," then bought back in—right before the crash.