Great question!! Different levels of gases in the atmosphere affect the spectrum we see, so I can see your thinking….but there are more than seven colours to the spectrum where they blend and “morph” into each other. Each color has a different wavelength. Red has the longest wavelength and violet has the shortest wavelength. When all the waves are seen together, they make white light.
No – because the visible spectrum is only a fixed part of the whole of the “electromagnetic spectrum”. The whole spectrum goes from cosmic rays (shortest wavelength, highest energy) though gamma rays, x-rays, ultra-violet, visible, infra-red, radar radio and television waves (longest wavelength, lowest energy). The visible part of the electromagnetic spectrum is less than 1,000,000,000,000,000,000th of the whole range