Since I'd studied piano, this was somewhat easier for me to read than an orchestral score, but I wanted to follow the individual parts. So, I tried making the notes for each instrument a different color:
This was better, but there wasn't enough color on the page to make it easy to follow a single part -- especially when a slow-moving part with just a few long notes was buried under a fast-moving part with lots of notes. The long notes needed to be bigger. This led me to a notation in which each note is a bar of color.