Answer:
If you need to match paint for a repair, you can take a paint chip to a hardware store, and they can analyze it to mix paint for an exact match to the chip.
Light bulb manufacturers probably use spectrographic analysis to create bulbs that are rated warm, cool, etc.
Manufacturers of sunglasses probably analyze the intensity of light at different frequencies (colors) that are transmitted by the glasses.
Steel makers can measure the temperature of molten metal in a furnace using  a radiometer.
