The actual wavelength for light is very short, about 500 billionths of a meter for red light, to about 300 billionths of a meter for blue light. That means for red light alone you could fit about 2 million wavelengths of light in a single meter. If all wavelengths are shown then you'll have a band of colour like we see below. You can see what appear to be dark lines and bright lines superimposed on the continuum. These bright and dark lines are like a fingerprint to astronomers, who know that particular bright or dark lines represent specific chemical elements.
Bright lines mean that something is luminous at a particular, pure colour.
The colour of the fluorescent bulb can be adjusted by using different gases, or operating the bulb at a different pressure. This is why some streetlights will look reddish while others will look white. White streetlights put out specific colours, but there is enough light being produced in red, green and blue parts of the spectrum that the overall effect is white light. A hot layer in the sun provides the continuum, while cooler atoms above it redirect the light at specific wavelengths away from us. As a star moves towards us, these lines seem to shift to the blue.