Emission nebulae are one of the 5 types of nebulae.
Emission nebulae are clouds of plasma, that give off different colors. These clouds are extremely hot, unlike normal nebula. The clouds are powered by a nearby star, which is makes the dust and clouds very hot and radiating.
Some methods used to study interstellar dust, is to observe through telescopes. They some times enhance the picture to see the real color of the nebula. Other methods, sometimes study the stars inside the nebula.