About a year ago, I was curious to see how the colors in LEGO had changed over the years. That is, as a kid, I remember grey bricks
being pretty rare (I had a bunch of grey plate from space ships, but only a few bricks), until 1984 when the castle sets came out. And now, grey is everywhere. Similarly, dark grey and brown were only occasionally used, until they started becoming more common in the late 1990s and early 2000s.
So, I did what I always seem to do-- I wrote a program to do some analysis. Using BrickLink inventories, and ignoring things like DUPLO, Fabuland, and Dacta/Education, I tried to do a breakdown by year from 1975 - present (then 2014). Here's what I found:
I haven't tried doing an updated one yet, but I may give it a go. I know there are a few colors like Dark Tan which are quickly becoming much more mainstream. And there are enough colors now such that the pie graphs probably aren't the best way to represent these!