What I love about colour is the fact that there is always something new to learn. Today I learned that the experiment with two prisms (often attributed to Newton) where he split white light with one prism and recombined it with a second (inverted) prism is not possible. There is a fantastic youtube video about this that shows that you need a lens between the two prisms to make this work.
https://www.youtube.com/watch?v=uucYGK_Ymp0