MY fave is one called Yves klein blue. Blue is a wonderful colour in itself because it is super energetic, so can cause some pretty cool effects. Purple light is nearly blue, and that is what makes us tan in the sun (UV). Yves Klein blue is a beautiful shade of blue that looks extra bright because all the molecules are separated from one another- it is very very pure. Blue inks also conduct electricity really well, which is my favourite property!
My favourite is probably blue. You see blue light in a lot of cool and weird phenomena – like something Cherenkov radiation, which is when electrons travelling really fast slow down by emitting light! This happens a lot in nuclear reactors – look for pics on google they are so cool.