Every other aspect of the interface in ES2 is color coded, but strangely enough luxuries are not. I made this cheat sheet for people who want to quickly reference or learn which luxuries are tied to which resource as well as their tier.
Also of note: Resource types are listed clockwise from most important (Industry, Orange, 0 degrees) to what I consider least important (Manpower and Trade, Dark Grey/Grey, 270/315 degrees). Manpower and Trade related resources are the outlyers and do not follow the key (bottom right).
Click to enlarge...