The color makeup of a fluorescent light, imaged through a spectrometer made of folded paper and a chunk of DVD. You can print and fold your own for free following the instructions here (they also have a kit, which is what I used).
The DVD chunk does all the work, by acting like a prism to spread out light into the colors that make it up. DVDs are constantly making rainbows out of white light, an unintentional byproduct of the microscopic data-storing grooves in their surface (this kind of light-spreading is called diffraction). The rest of the paper spectrometer just holds the DVD in the proper position so that it projects the rainbow from a single light source directly onto your eyeball or camera. More details (and a diagram) here.
The foldable spectrometer does produce cleaner spectra than this, if I improve the aim and close some of the gaps in the housing… I just thought the extra light looked kinda cool. If you want to go completely wild with scattered spectra everywhere, get a pair of diffraction glasses.