Bear with me. I took an intensive course in college called 'instructional design' (i.e. how people learn) about 22 years ago. Computers then hadn't caught up yet, and I'm waaay behind the times technologically.
If you can crack the color coding 'code', I'd suggest a rainbow effect for the decades;
Red = Current, post 2000
Orange = 1990's
Yellow = 1980's
Green = 1970's
Blue = 1960's
Purple = 1950's
Now's the time to make suggestions before you're too far into your project.
Edited by Likely Guy, 10 September 2012 - 04:16 AM.