Kirchhoff and Bunsen were fascinated by how different elements glow different colors when you put them in a flame, like stick some table salt in there and you'll get a bright yellow flame.

基尔霍夫和本森着迷于不同的元素在火焰中如何发出不同的颜色，就像在火里面放一些食盐，你会得到一个亮黄色的火焰。